Dynamic crystallization process temperature control system and method

Abstract

The embodiment of the invention provides a dynamic crystallization process temperature control system and method, and relates to the technical field of dynamic crystallization process control technologies. The method comprises the following steps: carrying out gradient cooling on feed liquid according to a preset first curve so as to enable the feed liquid to enter a metastable region; applying an ultrasonic pulse to the feed liquid at a preset time point when the feed liquid is in the metastable region so as to induce synchronous nucleation; and after the ultrasonic pulse is applied, carrying out first cooling treatment to control crystal growth. According to the invention, the problem of low crystallization quality is solved, so that the effect of improving the crystallization quality is achieved.

Description

Technical Field

[0001] The present invention relates to the field of dynamic crystallization process control, and more specifically, to a dynamic crystallization process temperature control system and method. Background Technology

[0002] Lithium hexafluorophosphate (LiPF6) is a core solute in lithium-ion battery electrolytes, and its purity, particle size distribution, and other physicochemical properties directly affect the battery's electrochemical performance, cycle life, and safety. In the industrial production of lithium hexafluorophosphate, crystallization is a crucial purification step that determines the quality of the final product. Current technologies commonly employ a constant-temperature cryogenic crystallization process, where a high-temperature saturated solution is directly placed in a crystallization vessel cooled by a cryogenic refrigerant at -50°C for rapid cooling.

[0003] However, while the large temperature difference provides a strong driving force for crystallization, it also leads to extreme local supersaturation near the reactor wall, causing explosive non-uniformity in crystal nuclei. This results in a wide particle size distribution, low purity, and poor batch-to-batch stability in the final product. Simultaneously, severe scaling on the reactor wall significantly reduces production efficiency and increases equipment maintenance costs. Even though some improved solutions employ programmed cooling and ultrasonic-induced nucleation, their control methods are still mostly open-loop control based on preset timetables. This cannot respond in real time to the actual changes in the nucleation state within the feed solution, and it has poor adaptability to disturbances such as batch-to-batch differences in raw material concentration and the influence of trace impurities. There is still a risk that insufficient or excessive ultrasonic application time may lead to incomplete nucleation or secondary crystal breakage.

[0004] There is currently no good solution to the above problems. Summary of the Invention

[0005] This invention provides a dynamic crystallization process temperature control system and method to at least solve the problem of poor crystal quality in related technologies.

[0006] According to an embodiment of the present invention, a method for controlling the temperature of a dynamic crystallization process is provided, comprising: According to the preset first curve, the liquid is subjected to gradient cooling so that the liquid enters the metastable region; At a predetermined time point when the liquid is in the metastable region, ultrasonic pulses are applied to the liquid to induce synchronous nucleation. After the ultrasonic pulse is applied, a first cooling process is performed to control crystal growth.

[0007] In an exemplary embodiment, the gradient cooling according to a preset first curve includes: Before applying the ultrasonic pulse, the temperature is reduced at a first cooling rate. After the ultrasonic pulse is applied, cooling is performed at a second cooling rate, wherein the first cooling rate is not equal to the second cooling rate.

[0008] In one exemplary embodiment, the method further includes, prior to applying the ultrasonic pulse: Obtain the current real-time temperature of the liquid feed; Determine whether the current real-time temperature is within the preset nucleation temperature window; When the current real-time temperature is within the preset nucleation temperature window, an ultrasonic pulse is applied to the liquid material to induce synchronous nucleation.

[0009] In one exemplary embodiment, after performing the first cooling process to control crystal growth, the method further includes: The temperature of the liquid material is maintained at a preset target temperature and the maturation time is continued for a preset duration to perform a maturation treatment on the crystals.

[0010] In one exemplary embodiment, applying an ultrasonic pulse to the feed liquid at a preset time point when the feed liquid is in the metastable region further includes: Real-time monitoring of the current temperature of the liquid feed; Based on the time series data of the current real-time temperature, calculate the time change rate of the current real-time temperature; Based on the trend of the change rate over time, the occurrence information of the exothermic crystallization event is determined; In response to the occurrence of the exothermic crystallization event, the application adjustment operation of the ultrasonic pulse is performed.

[0011] In an exemplary embodiment, determining the occurrence information of the exothermic crystallization event based on the trend of the time change rate includes: When the value of the time change rate changes from a negative value to a first positive value, or when the value of the time change rate is greater than a preset negative threshold, it is determined that the crystallization exothermic event has occurred; wherein, the first positive value is greater than the preset positive threshold.

[0012] According to another embodiment of the present invention, a dynamic crystallization process temperature control system is provided, comprising: The dynamic temperature control module is used to adjust the refrigerant temperature according to the set temperature value; An ultrasonic module includes an ultrasonic transducer for applying ultrasonic energy to the liquid feed. The central control module is communicatively connected to both the dynamic temperature control module and the ultrasonic module, and is used to execute the aforementioned method.

[0013] In one exemplary embodiment, the central control module further includes: The exothermic detection subunit is used to receive the current real-time temperature, calculate its rate of change over time, and determine the occurrence information of the exothermic crystallization event based on the trend of the rate of change over time, so as to obtain the nucleation completion signal. The nucleation completion signal is used to instruct the ultrasonic module to terminate or adjust its energy output.

[0014] According to yet another embodiment of the present invention, a computer-readable storage medium is also provided, wherein a computer program is stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed.

[0015] According to yet another embodiment of the present invention, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0016] This invention achieves temporal and spatial synchronization and homogenization of the nucleation process by applying ultrasonic pulses within a precise process window, ensuring uniform generation of crystal nuclei in the liquid phase of the material. This guarantees the concentration of the particle size distribution of the final product from the source, thus solving the problem of poor crystal quality and improving crystal quality. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of a dynamic crystallization process temperature control system according to an embodiment of the present invention; Figure 2 This is a flowchart of a dynamic crystallization process temperature control method according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the first curve according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the first curve according to Embodiment 2 of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] Furthermore, in this application, directional terms such as "upper," "lower," "left," and "right" may be defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and may change accordingly depending on the orientation of the components in the accompanying drawings.

[0021] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to an electrical connection that enables signal transmission.

[0022] As used herein, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from the given value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the given quantity (i.e., the limitations of the measurement system).

[0023] In a specific implementation, this method coordinates the dynamic temperature control module and the ultrasonic module through a central control module, thereby enabling precise timing control of the cooling rate, nucleation timing, and crystal growth environment during the crystallization process. This solves the technical problems of uncontrollable nucleation process, low crystal quality, and severe equipment wall sludge caused by one-step cooling with a fixed deep cryogenic refrigerant in the prior art. It achieves intelligent regulation of the crystallization process and ultimately obtains high-quality crystal products.

[0024] Example 1 Reference Figure 1 This embodiment provides a dynamic crystallization process temperature control system, which includes a crystallization vessel 110, a dynamic temperature control module 120, an ultrasonic module 130, a central control module 140, and a process monitoring module 150.

[0025] The crystallization vessel 110 is a reaction vessel that carries out the crystallization process. Its main body can be made of materials resistant to hydrofluoric acid corrosion, such as Hastelloy C-276 or 316L stainless steel lined with polytetrafluoroethylene (PTFE). The outer wall of the crystallization vessel 110 is equipped with a jacket 111 for circulating the refrigerant provided by the dynamic temperature control module 120 to achieve indirect heat exchange with the liquid inside the vessel. The crystallization vessel 110 can also be equipped with a stirring device 112 to maintain uniform mixing of the liquid during the crystallization process and prevent crystal sedimentation and agglomeration. This device can be an anchor-type or a paddle-type stirring blade.

[0026] The dynamic temperature control module 120 can be an integrated temperature control unit (TCU) used to adjust the temperature of its outlet refrigerant based on the real-time temperature setpoint from the central control module 140. The dynamic temperature control module 120 integrates a compressor refrigeration system 121, an electric heating system 122, a heat exchanger 123, and a circulating pump 124. The heat exchanger 123 can be a plate heat exchanger. The dynamic temperature control module 120 continuously monitors its outlet refrigerant temperature through its internal PID controller, compares the monitored outlet refrigerant temperature with the received setpoint, and then dynamically adjusts the workload of the refrigeration compressor or the power of the electric heater to ensure that the temperature of the refrigerant delivered to the jacket 111 is highly consistent with the setpoint, achieving a control accuracy of ±0.5℃.

[0027] The ultrasonic module 130 is used to apply high-frequency mechanical energy to the liquid material at specific stages of the crystallization process. Specifically, the ultrasonic module 130 includes an ultrasonic generator 131 and at least one ultrasonic transducer 132. The ultrasonic generator 131 is responsible for generating high-frequency electrical signals and can adjust the power and start / stop of the output signal according to the instructions of the central control module 140. The ultrasonic transducer 132 is used to convert high-frequency electrical energy into mechanical vibration of the same frequency. This transducer can be made of piezoelectric ceramic material. For example, the ultrasonic transducer 132 can be an insertion probe that extends into the liquid material from the top or side wall of the crystallization vessel 110 to ensure efficient coupling of ultrasonic energy. To prevent corrosion and crystal adhesion, the part of the transducer 132 in contact with the liquid material can be coated with PTFE.

[0028] The process monitoring module 150 is used to acquire key state parameters during the crystallization process in real time. In this embodiment, the process monitoring module 150 includes a temperature sensor 151 of a sheathed Pt100 platinum resistance thermometer. The temperature sensor 151 is installed inside the crystallization vessel 110, with its sensing end placed in the core area of ​​the liquid material, for measuring the real-time temperature of the liquid material, i.e., the current real-time temperature. In use, the temperature sensor 151 converts the resistance signal into a standard 4-20mA current signal through the temperature transmitter and sends it to the central control module 140.

[0029] The central control module 140 is responsible for the automated execution, monitoring, and safety management of the entire process. In this embodiment, the central control module 140 can be a Siemens S7-1500 series industrial-grade programmable logic controller (PLC). The hardware configuration of the central control module 140 includes a central processing unit (CPU), program and data memory, and several input / output (I / O) modules, including an analog output module for sending control commands to the dynamic temperature control module 120 and the ultrasonic module 130, a digital output module for controlling the start and stop of the ultrasonic module 130, and an analog input module for receiving feedback signals from the process monitoring module 150. The central control module 140 communicates with each functional module through industrial Ethernet such as Profinet or Modbus RTU fieldbus.

[0030] The central control module 140 contains a control program embedded in its memory, and stores a structured process parameter model (SPPM) to guide specific production batches. The SPPM includes not only a first curve table indicating the process path, but also encapsulates key threshold parameters such as the nucleation temperature window for decision-making and safety checks. In addition, it integrates a fault diagnosis submodule and a heat dissipation detection subunit. The fault diagnosis submodule continuously monitors the feedback signal from the temperature sensor 151, checking whether the signal is within a reasonable physical range and whether its dynamic rate of change conforms to logic to determine if the sensor or actuator is faulty, thereby ensuring the system's robustness.

[0031] Reference Figure 2 This application also provides a method for controlling the temperature of a dynamic crystallization process, which will be described below in conjunction with... Figure 1 The system shown provides a detailed explanation of the specific steps of this method.

[0032] S100, according to the preset first curve, uses the dynamic temperature control module 120 to perform programmed gradient cooling of the liquid so that the liquid enters the preset stable zone.

[0033] Before performing cooling, initialization is required: S110, process loading parameters.

[0034] The operator selects and loads a structured process parameter model file (SPPM) for the current production task through a human-machine interface (HMI) connected to the central control module 140. This model is a data structure that contains not only a timing control table consisting of multiple time-temperature-power data points, but also defines a set of key threshold parameters for nucleation control, including the starting temperature of the nucleation temperature window. and the end temperature The central control module 140 loads this model into its internal dedicated data block, which serves as the sole basis for all subsequent automated operations.

[0035] For example, the data structure of the timing control table can be a two-dimensional array or a list of lists, such as: [t=0 min, T=-2℃, P=0 W] [t=15 min, T=-5℃, P=0 W] [t=48 min, T=-23℃, P=250 W] [t=50 min, T=-23.6℃, ​​P=0 W] [t=70 min, T=-35℃, P=0 W] [t=140 min, T=-35℃, P=0 W] In addition, the model also includes key threshold parameters, such as , After loading the model, the PLC reads these data points and thresholds into its internal storage area for subsequent interpolation calculations and logical judgments. The entire loading process is completed through the HMI interface: the operator selects the process formula file corresponding to the product specification in the menu, clicks the "Load" button, and the HMI sends the file to the PLC's CPU via industrial Ethernet. The CPU executes the preset program block to parse the data and store it in the specified data block DB, and returns a confirmation signal for successful loading. This process usually takes between 1 and 2 seconds, ensuring the speed and accuracy of production startup.

[0036] S120, Feeding and Preparation.

[0037] The high-temperature lithium hexafluorophosphate solution, which has been processed in the previous stage and is in a saturated or slightly supersaturated state, is pumped into the crystallization tank 110 through pipelines until the liquid level reaches the preset working height. At this time, the central control module 140 confirms that all relevant valves are in the correct state, and the stirring device 112 starts at a low speed.

[0038] For example, assuming the target working volume is 1000 liters, the operator sets the feed rate to 1000L on the HMI. The PLC first checks whether valves V1 (feed valve) and V2 (vent valve) related to the feed line are open, and whether valve V3 (discharge valve) is closed. After confirming that everything is correct, the PLC starts the feed pump P1 and monitors the flow meter F1 and the level gauge L1. When the reading of the level gauge L1 reaches 1000L or the cumulative flow of the flow meter F1 reaches 1000L, the PLC stops the feed pump P1 and closes valves V1 and V2. Subsequently, the PLC issues a command to start the agitator 112, setting its speed to 30 RPM (revolutions per minute) to ensure uniform mixing of the liquid without excessive shearing.

[0039] S130, System pre-run self-test.

[0040] Before officially starting the cooling process, the central control module 140 performs a mandatory self-test procedure, during which the fault diagnosis submodule reads the current real-time temperature from the temperature sensor 151. The system checks whether the value is within a reasonable physical range, such as 0°C to 100°C, to rule out hardware faults such as open circuit (corresponding to extremely low readings) or short circuit (corresponding to extremely high readings) in the sensor signal. If the check passes, the system enters a standby state; otherwise, an alarm message is displayed on the HMI and the startup process is prohibited to prevent catastrophic operations based on error feedback.

[0041] For example, before starting the cooling program, the PLC's fault diagnosis submodule reads the value converted by the temperature sensor 151 through the analog input module. Assuming the initial temperature of the liquid is 60℃, the corresponding 4-20mA signal should be 4 + (60-0) / (100-0) × (20-4) = 13.6mA. Subsequently, the fault diagnosis logic checks whether this current value is between 4mA (corresponding to 0℃) and 20mA (corresponding to 100℃). If the reading is 3.5mA (below the lower limit of the range) or 20.5mA (above the upper limit of the range), the system determines that the sensor is faulty, triggers alarm "E-01: Liquid temperature sensor signal abnormality", displays a red flashing warning on the HMI, and locks the start of all power equipment (such as TCU and agitator) until the fault is eliminated.

[0042] After initialization and self-test are completed, such as Figure 3 As shown, the central control module 140 starts its internal process timer, denoted as t=0. It then reads the refrigerant temperature setpoint corresponding to the first time point (t=0) from the timing control table in the loaded SPPM model. Subsequently, the setpoint is converted into a corresponding control signal (e.g., a 4-20mA current signal) via its analog output module and sent to the dynamic temperature control module 120. The dynamic temperature control module 120 then activates its internal refrigeration and circulation system according to this instruction, adjusting and stabilizing the outlet refrigerant temperature at the initial setpoint. Afterward, the central control module 140 enters the main control loop; in this loop, it continuously performs the following tasks at a fixed control cycle (e.g., 1 second): First, based on the current value of the internal timer t, the precise refrigerant temperature setpoint for the current moment is calculated by performing linear interpolation between adjacent data points in the timing control table. The temperature is continuously sent to the dynamic temperature control module 120; since the temperature in the timing control table decreases gradually over time, the refrigerant temperature provided by the dynamic temperature control module 120 also decreases linearly and gradually. Secondly, the fault diagnosis submodule continuously monitors the temperature from the temperature sensor 151. It not only checks the validity of the numerical values, but also calculates... Rate of change over a short period of time (e.g., 60 seconds) During the gradient cooling phase, the rate of change should be a stable negative value. If the rate of change is detected to be close to zero for an extended period, while the TCU is still receiving cooling commands normally, it can be determined that the sensor reading is stuck or the TCU cooling system has failed. The system will immediately trigger an alarm and suspend the entire process. In this embodiment, because the refrigerant temperature decreases slowly, the huge local temperature difference caused by a sudden drop in the reactor wall temperature in traditional processes is avoided. The liquid inside the reactor, as a whole, also experiences a gradual and uniform temperature decrease, gradually entering the metastable region. The metastable region is characterized by the fact that although the supersaturation of the solution is sufficient to support crystal growth, it is not enough to spontaneously form a large number of crystal nuclei. This allows the entire reaction system to be controllably guided to a "ready-to-go" state.

[0043] For example, suppose the first few data points of the timing control table in the loaded SPPM model are: [t=0 min, T=-2℃, P=0 W] [t=15 min, T=-5℃, P=0 W] At t=0, the central control module 140 sends a setpoint of -2℃ to the dynamic temperature control module 120; at t=7.5 minutes, the central control module 140 calculates the current setpoint using linear interpolation. This new setting is then sent to the dynamic temperature control module 120, and so on.

[0044] Throughout the entire cooling phase, the power setting of the ultrasonic module 130 remained at 0W, i.e., it was kept off. The cooling rate during this phase was precisely controlled. This ensures minimal temperature gradients throughout the reactor, allowing for uniform accumulation of supersaturation across the entire liquid volume. This fundamentally avoids the problem of nucleation concentrating on the overcooled reactor wall surface, a problem common in traditional processes. During this process, the fault diagnosis submodule continuously analyzes... Time series data. If the data measured within the minute from t=5 minutes to t=6 minutes... If the temperature decreases linearly from -2.8℃ to -3.0℃, the calculated rate of change is -0.2℃ / min, which matches the set value, indicating the system is functioning normally. If the measured temperature remains at -2.8℃ with a rate of change of 0, the system is considered abnormal and the process is paused.

[0045] S200, at a preset time point when the liquid is in the metastable region, applies ultrasonic pulses to the liquid through an ultrasonic module to induce synchronous nucleation.

[0046] In the ideal metastable region, the nucleation process is triggered by the intervention of external energy. Specifically, it can be broken down into the following sub-steps: S210, Process condition safety inspection.

[0047] The central control module 140 continuously performs dual condition checks in its main control loop: Determine whether the internal timer t has reached the preset time point for starting the ultrasonic wave in the timing control table. ; Determine the current real-time temperature from temperature sensor 151. Whether the preset nucleation temperature window has been entered, i.e., to determine Is it less than the nucleation window initiation temperature? .

[0048] Only when both conditions are met simultaneously will the central control module 140 generate an ultrasonic trigger permission signal, allowing the process to proceed to the next sub-step. This dual interlocking mechanism greatly enhances the safety and robustness of the process, ensuring that critical nucleation operations only occur within the most suitable process window, avoiding accidental ultrasonic triggering at incorrect temperatures due to equipment delays or thermal conduction lags.

[0049] For example, suppose the nucleation-related parameters defined in the SPPM model are: , At t=47 minutes, even though the temperature inside the vessel has reached -16.0℃ (meeting the temperature condition), the PLC will not generate an ultrasonic trigger permission signal because the time condition (t>48 minutes) is not met. However, at t=48 minutes, the timer condition is met, and the PLC begins checking the temperature condition. If the measured temperature at this time... If the temperature is -14.5℃, the temperature condition is not met, and the signal is still suppressed. Only when the timer t > 48 min and When both conditions are true, the internal logic relay Q0.1 is set to 1, indicating that the trigger permission has been generated, and the program flow jumps to S220.

[0050] S220, drives the ultrasonic module.

[0051] Upon receiving the ultrasonic trigger authorization signal, the central control module 140 immediately executes the drive operation. It reads from the timing control table. Non-zero ultrasonic power setting value at time [time] Subsequently, it sends a high-level start signal to the remote control terminal of the ultrasonic generator 131 via its digital output module; simultaneously, it transmits the power setting value via its analog output module. It is converted into a corresponding current signal (e.g., 4-20mA) and sent to the power adjustment input of the ultrasonic generator 131.

[0052] S230, nucleation induced by ultrasonic cavitation effect.

[0053] Upon receiving the start and power setting signals, the ultrasonic generator 131 immediately drives the ultrasonic transducer 132 to operate. The transducer 132 generates high-frequency (e.g., 20kHz to 40kHz) mechanical vibrations on its surface and transmits this vibrational energy to the liquid, forming a high-frequency pressure wave. During the negative pressure half-cycle of the pressure wave, tiny gas nuclei in the liquid are stretched and expanded to form cavitation bubbles. These cavitation bubbles are rapidly compressed during the subsequent positive pressure half-cycle until they collapse. At the moment the cavitation bubbles collapse, a temperature of several thousand degrees Celsius and a pressure of several hundred atmospheres are generated in the extremely small volume of liquid around them. This provides enormous local energy for the formation of crystal nuclei, thereby greatly reducing the nucleation energy barrier. Meanwhile, because the ultrasonic energy is uniformly distributed throughout the liquid phase of the feed, the nucleation process induced by the cavitation effect occurs simultaneously in hundreds of millions of micro-regions throughout the entire reactor. This results in a large number of crystal nuclei being generated synchronously and uniformly in the liquid phase of the feed within a very short time (usually within seconds), rather than being generated on the reactor wall. The macroscopic manifestation of this is a significant instantaneous increase in the turbidity of the originally clear feed liquid.

[0054] S240, adaptive ultrasonic control based on exothermic crystallization events.

[0055] In the classic implementation, the ultrasonic wave is stopped based on a preset time point; however, in this embodiment, the synchronous formation of large-scale crystal nuclei releases a large amount of latent heat of crystallization instantaneously, and this heat flow temporarily changes the temperature drop curve of the liquid material; at this time, the heat release detection subunit inside the central control module 140 regulates the process through the following sub-steps: S241, High-frequency temperature monitoring and rate of change calculation.

[0056] Simultaneously with the activation of the ultrasonic pulse, the heat release detection subunit increases the sampling frequency of the temperature sensor 151 from the conventional 1Hz to 10Hz; and for each acquired temperature value... This module calculates the rate of change of temperature over time (i.e., the first derivative) within a sliding time window (e.g., a window width of 10 seconds containing 100 data points) using numerical methods (such as least squares fitting). Before nucleation, due to the continuous cooling effect of the dynamic temperature control module, It should be a relatively stable negative value, the magnitude of which is determined by the set cooling rate.

[0057] For example, assuming that after the ultrasonic wave is activated, the system is in steady-state cooling with a cooling rate of -0.2℃ / min, or -0.0033℃ / s; the heat release detection subunit at time point... The collected 10-second window data is Linear regression analysis was performed on these data points and their corresponding time points: The slope that can be obtained That is Under steady state, The value will fluctuate around -0.0033. This submodule then continues to calculate... This is to form a time series of the rate of change.

[0058] S242, Identification of exothermic event features and determination of nucleation completion.

[0059] When ultrasound-induced nucleation occurs on a large scale, the release of latent heat of crystallization significantly offsets the external cooling effect, which is macroscopically manifested as follows: The rate of decline suddenly slows, and may even briefly rebound; this change is reflected in... The above indicates that its value will rapidly increase from its original stable negative value (i.e., the absolute value decreases), or even become positive; thus, the heat release detection subunit identifies... The logic for identifying this characteristic inflection point in a time series can be set as follows: when The increment of the value over a short period of time (e.g., 2 seconds). Exceeding the preset trigger threshold At that time, it is determined that an exothermic crystallization event has occurred, marking the completion of the nucleation process; threshold It can be calibrated experimentally, for example, by setting it to 50% of the absolute value of the steady-state cooling rate.

[0060] For example, assuming a steady-state cooling rate of -0.0033℃ / s, the trigger threshold... Can be set to At t=49 minutes and 00 seconds, the calculated The value was -0.0032℃ / s; in subsequent monitoring, The sequence is: [-0.0032, -0.0033, -0.0031, -0.0020, -0.0005, +0.0015, ...], that is, within the 2 seconds from t=49 minutes 03 seconds to t=49 minutes 05 seconds, The value jumped from -0.0031 to -0.0005, an increment of 0.0026, due to... The exothermic detection subunit immediately determines that the nucleation process has been effectively completed and generates an internal flag indicating "nucleation complete".

[0061] S243, adaptive termination or modulation of ultrasound.

[0062] Once the nucleation completion flag is set, the central control module 140 immediately executes a preset response action, such as terminating the ultrasonic wave. Specifically, the central control module 140 immediately cancels the control signal to the ultrasonic generator 131, that is, sets the digital output signal to a low level and restores the analog output power setting to the current signal corresponding to 0W. Furthermore, the response action can be to modulate the ultrasonic power. For example, after detecting a heat release event, instead of stopping immediately, the ultrasonic power is linearly or stepwise reduced from the initial 250W to a lower sustaining power (e.g., 50W) and maintained for a short period (e.g., 10 seconds) to ensure that all potential crystal nuclei are activated before completely stopping. This adaptive and event-feedback-based control ensures that the ultrasonic treatment time meets the nucleation requirements, avoiding mechanical damage (i.e., secondary breakage) to already formed fragile crystal nuclei caused by excessively long ultrasonic treatment, thereby fundamentally guaranteeing the concentration of the final product's particle size distribution.

[0063] S250, stop ultrasound.

[0064] In a conventional embodiment that does not employ the aforementioned adaptive control strategy, the central control module 140 continuously times the time until t reaches the ultrasonic end time point set in the timing control table. At this time, it immediately cancels the control signal to the ultrasonic generator 131; specifically, it sets the digital output signal to a low level and restores the power setting value of the analog output to the current signal corresponding to 0W. At this time, the ultrasonic module 130 stops working, and the ultrasonic pulse application is completed. The duration of this pulse must be sufficient to provide enough energy to complete the nucleation process, while also avoiding excessively long application time that could cause mechanical damage to the already formed fragile crystal nuclei.

[0065] For example, suppose the nucleation-related parameters defined in the SPPM model are: , , The corresponding data points in the timing table are [t=48min, T=-23℃, P=250W] and [t=50min, T=-23.6℃, ​​P=0W]. When the system timer reaches t=48 minutes, the safety check is initiated. The central control module 140 reads the actual temperature inside the reactor at this time. The temperature is -20.5℃, suitable for temperatures between -20.5℃ and -15.0℃. Since the temperature condition is met, the ultrasonic module is immediately activated, sending a start signal to the ultrasonic generator 131 and setting the power to 250W. Assuming its analog output is 4-20mA, corresponding to a power range of 0-500W, the output current is... Subsequently, the ultrasonic transducer 132 operates at a power of 250W for 2 minutes. During these 2 minutes, intense and uniform nucleation occurs inside the vessel. When the timer reaches t=50 minutes, the central control module 140 sets the digital output of the ultrasonic generator 131 to OFF, and the analog output is restored to 4mA, thus ending the ultrasonic-induced nucleation stage.

[0066] After the ultrasonic pulse is applied, the S300 continues to cool down in a programmed manner through a dynamic temperature control module to control crystal growth.

[0067] This step provides a stable and controlled growth environment for the numerous uniform crystal nuclei generated, ensuring they grow at an appropriate rate to form high-quality crystals with well-defined structures and few inclusions. Specifically, in Afterwards, the central control module 140 continues its main control cycle, that is, it continuously searches for and calculates the corresponding refrigerant temperature setpoint from the timing control table based on the current value of timer t. The temperature is then sent to the dynamic temperature control module 120. At this stage, the cooling rate defined by the first curve (i.e., the second cooling rate) can differ from the cooling rate of the previous stage (the first cooling rate). Typically, to improve production efficiency while ensuring crystal quality, the cooling rate at this stage can be set slightly faster than in stage S100. Since a large number of crystal nuclei already exist in the solution as a growth substrate, the supersaturation of the solution is primarily consumed through molecular deposition on the surface of these nuclei, rather than being used to form new nuclei. The controlled cooling rate at this point means a controlled rate of supersaturation generation, which allows for effective control of the crystal growth rate, avoiding the problem of solvent or impurities being trapped inside the crystal due to excessively rapid growth, thus ensuring the high purity of the final product. Specifically, this includes the following sub-steps: S310, aged treatment.

[0068] After the crystal growth stage is completed, a ripening process is usually also included; for example, when timer t reaches a holding start point set in the timing control table. At that time, the temperature of the liquid also reached the preset final temperature. For a period of time thereafter (i.e., the curing time), the temperature setpoint in the timing control table will remain at [value missing]. Unchanged. Subsequently, the central control module 140 continuously sends data to the dynamic temperature control module 120. At this constant-temperature ripening stage, according to the Ostwald ripening principle, smaller crystals with higher surface energy in the system will dissolve, and the dissolved solute will deposit on the surface of larger crystals, causing the large crystals to grow further. This can effectively narrow the particle size distribution of the entire crystal group and improve the perfection of the crystals.

[0069] Finally, after the entire process (including cooling and curing) is completed, i.e., when timer t reaches the total process time... At this time, the central control module 140 sends a process completion signal and stops all control outputs; at this time, the crystallizer 110 contains crystal slurry with uniform particle size and high purity crystals, which is then transported to subsequent solid-liquid separation (such as centrifugation or filtration) and vacuum drying processes.

[0070] For example, after t=50 minutes, the timing control table might define the following data points: [t=70 min, T=-35℃, P=0 W] and [t=140 min, T=-35℃, P=0 W]; the cooling rate during the period from t=50 minutes to t=70 minutes is... This is the main growth time of the crystals; at t=70 minutes, the temperature of the liquid reaches the final -35℃; from t=70 minutes to t=140 minutes, the temperature setting is always maintained at -35℃, and this 70-minute period is the ripening time; during this period, the uniformity of the crystal particle size is further improved; when t=140 minutes, the entire crystallization process ends.

[0071] By implementing precise temperature control at different stages and rates, the entire crystallization process can be managed meticulously, effectively improving crystal quality.

[0072] The following is a complete numerical example of systematically optimizing core process parameters using a multi-factor orthogonal experimental design method.

[0073] In an exemplary optimization process, three process parameters that have the most critical impact on the crystallization result are selected as evaluation factors. These parameters are: Factor A, cooling rate before nucleation (unit: °C / min); Factor B, ultrasonic power (unit: W); Factor C, duration of ultrasound treatment (unit: s).

[0074] Based on preliminary exploratory experiments and empirical knowledge, three different levels were set for each factor to cover a reasonable range that might produce good results: Factor A (cooling rate): A1=0.5, A2=0.8, A3=1.1 (℃ / min) Factor B (ultrasonic power): B1=200, B2=250, B3=300 (W) Factor C (ultrasound time): C1=60, C2=90, C3=120(s) An L9(3^4) orthogonal array was selected to arrange the experiments, which allows for the examination of the main effects of three three-level factors in nine experiments. The experimental setup and the experimental results for a set of hypotheses are shown in Table 1 below, where the evaluation indicators are the average particle size D50 (in μm) of the final product and the relative standard deviation (RSD) of the particle size distribution (in %).

[0075] Table 1 Next, a range analysis was performed on the experimental results, using the evaluation index RSD (the smaller the better) as an example: Calculate the mean RSD of each factor at different levels: K(A1)=(18.2+14.5+15.8) / 3=16.17 K(A2)=(16.5+12.1+17.3) / 3=15.30 K(A3)=(19.5+13.5+14.2) / 3=15.73 K(B1)=(18.2+16.5+19.5) / 3=18.07 K(B2)=(14.5+12.1+13.5) / 3=13.37 K(B3)=(15.8+17.3+14.2) / 3=15.77 K(C1)=(18.2+17.3+13.5) / 3=16.33 K(C2)=(14.5+16.5+14.2) / 3=15.07 K(C3)=(15.8+12.1+19.5) / 3=15.80 Calculate the range R of each factor: R(A)=max(16.17,15.30,15.73)-min(16.17,15.30,15.73)=0.87 R(B)=max(18.07,13.37,15.77)-min(18.07,13.37,15.77)=4.70 R(C)=max(16.33,15.07,15.80)-min(16.33,15.07,15.80)=1.26 Based on the magnitude of the range (R(B)>R(C)>R(A)), the order of influence on RSD can be determined as follows: ultrasonic power > ultrasonic time > cooling rate.

[0076] Choose the optimal level: For RSD, we want its value to be as small as possible. Therefore, we choose the level with the smallest mean for each factor. According to the calculation results, the optimal level combination is A2 (0.8℃ / min), B2 (250W), C2 (90s); and so on.

[0077] Through similar analysis, the order of importance and optimal level of influence on D50 can be obtained (assuming we expect D50 to be between 200-250 μm). Considering both indicators comprehensively, a set of optimal process parameters is finally determined. For example, the final optimal process parameters are: a cooling rate before nucleation of 0.8℃ / min, an ultrasonic power of 250W, and an ultrasonic treatment time of 90s. These parameters, obtained through systematic optimization, are then incorporated into the SPPM model to guide large-scale industrial production.

[0078] This complete, data-driven optimization process provides those skilled in the art with a clear and repeatable method to determine the optimal process parameters, thereby ensuring the feasibility of the technical solution of this invention.

[0079] The system and method of this application innovatively integrate and coordinate advanced programmed temperature control technology with ultrasonic induction technology, and introduce an adaptive feedback control loop based on crystallization exothermics. This successfully transforms the traditionally experience-dependent and difficult-to-control industrial crystallization process into a predictable, repeatable, and optimizable intelligent production process, directly solving the core technical pain points in the production of high-purity lithium hexafluorophosphate and improving product quality.

[0080] Example 2 To address the common problems of mother liquor inclusion (i.e., impurities being trapped inside the crystal) and fine crystal agglomeration in the later stages of crystal growth, this application further includes the following steps: S301, Perform acoustic-thermal coupled oscillation growth process After the synchronous nucleation stage of S200 is completed, the central control module 140 does not directly execute the monotonous cooling logic, but instead enters a preset multi-level oscillation growth mode. This mode consists of several (e.g., 3-5) consecutive self-repair cycles, each of which is executed strictly according to the following timing sequence: S3011: Sound Field Decoupling like Figure 4 As shown, the central control module 140 drives the ultrasonic module 130 to output a short-duration, low-power depolymerization pulse. The corresponding power is set to 30%~50% of the nucleation power (e.g., 80W), and the duration is set to 15s. Since the low-energy sound field is insufficient to generate new nuclei (avoiding the risk of secondary nucleation), the shear force it generates is sufficient to break up the crystal aggregates that are weakly connected due to collisions during the growth process. At the moment the aggregates are broken up, the high-impurity concentration mother liquor that was originally wrapped in the gaps of the aggregates is released back into the bulk solution, thereby avoiding the situation of mother liquor entrapment.

[0081] S3012: Thermal pulse melting In response to the falling edge of the depolymerization pulse (i.e., the instant the ultrasound stops), the central control module 140 immediately controls the dynamic temperature control module 120 to execute a positive temperature pulse, that is, temporarily interrupt the cooling trend and control the refrigerant temperature to rise rapidly at a relatively fast rate (e.g., +3.0℃ / min). (For example, increase the temperature by 2.0°C) and maintain it for a short period of time (e.g., 3 minutes); when the system briefly enters the unsaturated region, according to the Gibbs-Thomson effect, the aforementioned tiny fragments and sharp protrusions (i.e., high-energy sites) on the surface of the large crystal have higher solubility and will therefore be preferentially melted away, thereby digesting the fine crystals in the system and smoothing out the surface defects of the main crystal.

[0082] S3013: Healing and Growth After the defect is eroded, the central control module 140 controls the dynamic temperature control module 120 to resume cooling, that is, to reduce the temperature at a slower rate (e.g. -0.5℃ / min) until the starting temperature or final end temperature of the next cycle is reached; the dissolved solute is redeposited in an orderly manner on the remaining smooth crystal surface, repairing the crystal lattice, increasing the crystal volume and making the structure more compact.

[0083] For example, suppose the oscillation mode begins at t=60 minutes, and the current temperature is -25°C: Turn on 80W ultrasound for 15 seconds to break up the clusters; Ultrasonication stops, at which point the TCU heats at full power, and the vessel temperature rises to -23°C within 1 minute to dissolve the fine powder and exposed impurities; Maintain -23°C to To address erosion defects; Start cooling at -0.5℃ / min until... The temperature is lowered to -28°C to allow for healing and growth.

[0084] The above process was repeated 3 times to reduce the content of internal inclusions by 90% compared to Example 1, and to achieve a single crystal integrity of over 99%.

[0085] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0086] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0087] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed.

[0088] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard disk, magnetic disk, or optical disk.

[0089] Embodiments of the present invention also provide an electronic device including a memory and a processor, the memory storing a computer program and the processor being configured to run the computer program to perform the steps in any of the above method embodiments.

[0090] In one exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0091] Through the above description of the embodiments, those skilled in the art can clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0092] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0093] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0094] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0095] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0096] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for temperature control in a dynamic crystallization process, characterized in that, include: According to the preset first curve, the liquid is subjected to gradient cooling so that the liquid enters the metastable region; At a predetermined time point when the liquid is in the metastable region, ultrasonic pulses are applied to the liquid to induce synchronous nucleation. After the ultrasonic pulse is applied, a first cooling process is performed to control crystal growth.

2. The method according to claim 1, characterized in that, The gradient cooling based on the preset first curve includes: Before applying the ultrasonic pulse, the temperature is reduced at a first cooling rate. After the ultrasonic pulse is applied, cooling is performed at a second cooling rate, wherein the first cooling rate is not equal to the second cooling rate.

3. The method according to claim 1, characterized in that, Before applying the ultrasonic pulse, the method further includes: Obtain the current real-time temperature of the liquid feed; Determine whether the current real-time temperature is within the preset nucleation temperature window; When the current real-time temperature is within the preset nucleation temperature window, an ultrasonic pulse is applied to the liquid material to induce synchronous nucleation.

4. The method according to claim 1, characterized in that, After the first cooling treatment to control crystal growth, the method further includes: The temperature of the liquid material is maintained at a preset target temperature and the maturation time is continued for a preset duration to perform a maturation treatment on the crystals.

5. The method according to claim 1, characterized in that, Applying ultrasonic pulses to the feed liquid at a preset time point when the feed liquid is in the metastable region also includes: Real-time monitoring of the current temperature of the liquid feed; Based on the time series data of the current real-time temperature, calculate the time change rate of the current real-time temperature; Based on the trend of the change rate over time, the occurrence information of the exothermic crystallization event is determined; In response to the occurrence of the exothermic crystallization event, the application adjustment operation of the ultrasonic pulse is performed.

6. The method according to claim 5, characterized in that, The information used to determine the occurrence of the exothermic crystallization event based on the trend of the rate of change over time includes: When the value of the time change rate changes from a negative value to a first positive value, or when the value of the time change rate is greater than a preset negative threshold, it is determined that the crystallization exothermic event has occurred; wherein, the first positive value is greater than the preset positive threshold.

7. A dynamic crystallization process temperature control system, characterized in that, include: The dynamic temperature control module is used to adjust the refrigerant temperature according to the set temperature value; An ultrasonic module includes an ultrasonic transducer for applying ultrasonic energy to the liquid feed. The central control module is communicatively connected to the dynamic temperature control module and the ultrasonic module, respectively, and the central control module is used to execute the method as described in any one of claims 1 to 6.

8. The system according to claim 7, characterized in that, The central control module also includes: The exothermic detection subunit is used to receive the current real-time temperature, calculate its rate of change over time, and determine the occurrence information of the exothermic crystallization event based on the trend of the rate of change over time, so as to obtain the nucleation completion signal. The nucleation completion signal is used to instruct the ultrasonic module to terminate or adjust its energy output.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program is configured to perform the method described in any one of claims 1 to 6 when executed.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method as described in any one of claims 1 to 6.

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