An adaptive freeze-drying process and system thereof

Abstract

The application discloses a kind of self-adapting freeze-drying processing method and system, belong to drying processing system technical field.It includes: the mapping relationship of material dielectric response and moisture content is established by broadband dielectric spectrum determination, and the collapse temperature limit value and safe heating rate are determined;Directional temperature gradient field is established in multi-temperature control zone freeze-drying cabin, and ice crystal directional growth is induced;Real-time monitoring of radio frequency impedance real part change rate, automatically switch to analytical heating mode at the end of sublimation and execute pulsating pressure differential cycle;The measured temperature is compared with the expected curve dynamically, and when the limit is exceeded, the heating power is automatically adjusted or the pulsating pressure differential parameters are adjusted;Low temperature plasma field is applied to cold trap to promote bound water removal;When dielectric parameters are stable and water vapor partial pressure is lower than threshold value, drying is completed.The method realizes intelligent adaptive control of the whole freeze-drying process, significantly improves drying efficiency, product quality and process stability.

Description

Technical Field

[0001] This invention belongs to the technical field of drying systems, specifically relating to an adaptive freeze-drying method and system. Background Technology

[0002] Freeze-drying is a key post-processing step for maintaining the integrity of the catalyst's three-dimensional porous framework and heterojunction interfaces.

[0003] Existing freeze-drying systems mostly employ a continuous evacuation mode to maintain a constant vacuum, which easily leads to the formation of stagnant gas films inside the material, insufficient mass transfer driving force, resulting in lengthy drying cycles and high energy consumption. Simultaneously, the integrated heating process cannot implement zoned thermal management for different drying stages, often resulting in overheating and sintering in dried areas and solvent residue in undried areas, severely degrading the exposure of active sites. Furthermore, existing cold traps only function as passive water-capturing units, lacking effective suppression of vapor back-diffusion and unable to decompose organic dispersants, sulfur- or nitrogen-containing volatile impurities in situ. These residues easily re-adsorb onto the catalyst surface, poisoning active sites or corroding vacuum pump oil. More critically, existing systems mostly rely on offline weighing or preset time sequences to determine the endpoint, lacking the ability to in-situ sense the local moisture content and sublimation front of the material, making it difficult to achieve closed-loop control based on real-time status.

[0004] Therefore, there is an urgent need to develop a freeze-drying system with in-situ sensing, zoned adaptive control, and in-situ purification functions. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide an adaptive freeze-drying method and system. This method utilizes a dielectric-thermal conductivity coupled array to invert the local moisture content and sublimation front position of the material in real time. Combined with a zoned adaptive mode switching mechanism, it achieves precise control over the drying process of the catalyst precursor, effectively suppressing capillary contraction, liquid bridge agglomeration, and local remelting collapse, significantly maintaining the continuity of the mesoporous-macroporous hierarchical structure and the integrity of the heterojunction interface bonding. Simultaneously, a pulsed pressure difference mass transfer driving module enhances diffusion mass transfer through periodic pressure fluctuations, shortening the drying cycle and reducing energy consumption. A plasma-activated cold trap efficiently captures water while decomposing trace organic and sulfur- and nitrogen-containing volatile impurities in situ, preventing poisoning of active sites. Combined with a tail gas heat recovery and solvent capture module, it achieves cold energy recycling and solvent recovery. After treatment by this system, the photocatalytic material exhibits significantly improved catalytic activity, product selectivity, and long-term stability in reactions such as CO2 reduction, nitrogen fixation, and pollutant degradation, showing broad industrial application prospects in environmental photocatalysis, energy catalysis, and the preparation of fine chemical catalysts.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an adaptive freeze-drying method, comprising the following steps: Broadband dielectric spectrum was measured on the material to be freeze-dried to establish a mapping relationship between dielectric response parameters and material moisture content, and the collapse temperature limit and safe heating rate of the material to be freeze-dried were determined based on the mapping relationship. The material to be freeze-dried is placed in a freeze-drying chamber with multiple independent temperature control zones. A directional temperature gradient field is established in each temperature control zone to induce ice crystals in the material to grow in a predetermined direction. The real part change trend of the radio frequency impedance of each temperature control zone is acquired in real time. When the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and a pulsed differential pressure cycle is performed on the temperature control zone to enhance mass transfer. The material temperature in each temperature control zone is collected in real time, and the material temperature is dynamically compared with the expected temperature curve generated based on the material thermal property model. When the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the heating power of the corresponding temperature control zone is adaptively reduced and / or the process parameters of the pulsating differential pressure cycle are adjusted. Applying a low-temperature plasma field to the cold trap region of the freeze-drying chamber reduces the partial pressure of water vapor on the surface of the cold trap, promoting the removal of bound water from the material. The freeze-drying process ends when the dielectric response parameters are stable and the water vapor partial pressure in the freeze-drying chamber is lower than a preset threshold.

[0007] In the step of performing broadband dielectric spectroscopy on the freeze-dried material, establishing a mapping relationship between the dielectric response parameters and the material moisture content, and determining the collapse temperature limit and safe heating rate of the material based on the mapping relationship, the established mapping relationship between the dielectric response parameters and the material moisture content is as follows:

[0008] in, , For calibration coefficients related to material type, It is the dielectric loss factor. The characteristic frequency is denoted as .

[0009] In the step of acquiring the real part change trend of the radio frequency impedance of each temperature control zone in real time, when the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and a pulsed pressure differential cycle is performed on the temperature control zone to enhance mass transfer. The pulsed pressure differential cycle includes a pumping and depressurization stage, a pressure holding stage, and an instantaneous pressure increase and depressurization stage executed in sequence.

[0010] In the step of real-time acquisition of material temperature in each temperature control zone, dynamic comparison of the material temperature with the expected temperature curve generated based on the material thermal property model, and adaptive adjustment of the heating power of the corresponding temperature control zone and / or adjustment of the process parameters of the pulsating differential pressure cycle when the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the method for generating the expected temperature curve based on the material thermal property model is as follows: Obtain the thermophysical property parameters of the material to be freeze-dried at different moisture contents, and establish a correlation model between the thermophysical property parameters and the moisture content; Using initial moisture content, target moisture content, collapse temperature limit, safe heating rate and chamber pressure as model boundary conditions, a one-dimensional unsteady heat transfer model along the material thickness direction is established, and heat transfer boundary conditions between the material and the shelf and the chamber gas are set. The corresponding thermophysical parameters are dynamically updated based on the moisture content and temperature of each layer of the material, and the temperature distribution of the material along the thickness direction at each moment is obtained iteratively using a numerical solution method. Extract the temperature values ​​at corresponding locations in each temperature control zone, and process them to form the expected temperature curve of each temperature control zone over time.

[0011] In the step of applying a low-temperature plasma field to the cold trap region of the freeze-drying chamber to reduce the partial pressure of water vapor on the surface of the cold trap and promote the removal of bound water inside the material, the low-temperature plasma field is applied intermittently using a dielectric barrier discharge method, with a discharge power of 5W to 20W and a duty cycle of 20%.

[0012] In a second aspect, the present invention provides an adaptive freeze-drying system, comprising: The mapping relationship establishment module is used to perform broadband dielectric spectrum determination on the freeze-dried material, establish a mapping relationship between dielectric response parameters and material moisture content, and determine the collapse temperature limit and safe heating rate of the material based on the mapping relationship. The pretreatment homogenization module is used to place the material into a freeze-drying chamber with multiple independent temperature control zones, establish a directional temperature gradient field in each temperature control zone, and induce ice crystals in the material to grow in a predetermined direction. The pulsed differential pressure mass transfer drive module is used to acquire the real part change trend of the radio frequency impedance of each temperature control zone in real time. When the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and the pulsed differential pressure cycle is performed on the temperature control zone to enhance mass transfer. An adaptive adjustment module is used to collect the material temperature of each temperature control zone in real time, and dynamically compare the material temperature with the expected temperature curve generated based on the material thermal property model. When the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the heating power of the corresponding temperature control zone is adaptively reduced and / or the process parameters of the pulsating differential pressure cycle are adjusted. The plasma-activated cold trap module is used to apply a low-temperature plasma field to the cold trap region of the freeze-drying chamber, reduce the water vapor partial pressure on the surface of the cold trap, and promote the removal of bound water from the material. The judgment module is used to end the freeze-drying process when the dielectric response parameters are stable and the water vapor partial pressure in the freeze-drying chamber is lower than a preset threshold.

[0013] The freeze-drying chamber of the pretreatment homogenization module is equipped with at least three independent temperature control zones. Each temperature control zone is equipped with an array of dielectric-thermal conductivity inductive heating plates. The heating plates integrate radio frequency impedance sensors and thin-film heat flow sensors. The radio frequency impedance sensors are used to invert the local moisture content of the material and the sublimation front position in real time.

[0014] The pulsed pressure differential mass transfer drive unit is connected to the freeze-drying chamber. The pulsed pressure differential mass transfer drive unit includes a main exhaust pipeline, one end of which is connected to the exhaust port of the freeze-drying chamber, and the other end is connected to the variable frequency vacuum pump. An intelligent butterfly valve is installed on the main exhaust pipeline. The intelligent butterfly valve has a built-in angular displacement sensor and a pressure feedforward controller for adjusting the valve opening.

[0015] The plasma-activated cold trap module is disposed on the surface of the cold trap coil of the freeze-drying chamber and is loaded with dielectric barrier discharge electrodes.

[0016] It also includes a tail gas heat recovery and solvent capture module, which includes a stepped condenser and an activated carbon-zeolite gel composite adsorption layer arranged sequentially along the airflow direction.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an adaptive freeze-drying method that uses a dielectric-thermal conductivity induction array to perform real-time non-invasive inversion of the local moisture content and sublimation front position of the material. Combined with a zoned adaptive mode switching mechanism, it achieves precise control over the drying process of the catalyst precursor. Compared with traditional oven drying or single continuous vacuum drying, it can effectively suppress the damage to the catalyst pore structure caused by capillary shrinkage, liquid bridge agglomeration, and local remelting collapse, significantly maintaining the continuity and openness of the mesoporous-macroporous hierarchical structure. At the same time, the zoned threshold judgment logic can implement differentiated thermal management for each temperature control zone at different drying stages, avoiding sintering of active components due to overheating in the dried zone or solvent residue caused by underheating in the undried zone. This effectively maintains the integrity of the heterojunction interface bonding, the confined distribution of metal clusters, and the highly exposed crystal surface structure.

[0018] Furthermore, the pulsed pressure difference mass transfer drive module breaks the stagnant gas film inside and on the surface of the material through periodic pressure fluctuations, enhances the diffusion mass transfer driving force of water vapor and organic solutes, significantly shortens the main drying and desorption drying cycles, and reduces overall energy consumption; while the plasma-activated cold trap captures water vapor, it intermittently applies low-temperature plasma to suppress the vapor back diffusion trend, and decomposes trace organic residues and sulfur- and nitrogen-containing volatile impurities in situ, avoiding poisoning of active sites and contamination of vacuum pump oil.

[0019] Furthermore, the exhaust gas heat recovery and solvent capture module enables the cascade condensation recovery and cold energy recycling of organic solvents, further reducing operating costs and exhaust gas emissions. After treatment by this system, the photocatalytic materials exhibit significantly enhanced catalytic activity, product selectivity, and long-term stability in reactions such as CO2 reduction, nitrogen fixation, and pollutant degradation, showing broad industrial application prospects in environmental photocatalysis, energy catalysis, and the preparation of fine chemical catalysts. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0021] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0022] Example 1 like Figure 1 As shown, an adaptive freeze-drying method includes the following steps: S1: Perform broadband dielectric spectrum determination on the material to be freeze-dried, establish a mapping relationship between dielectric response parameters and material moisture content, and determine the collapse temperature limit and safe heating rate of the material to be freeze-dried based on the mapping relationship.

[0023] Broadband dielectric spectroscopy was performed on the material to be freeze-dried. The preferred frequency range for the broadband dielectric spectroscopy was 10 Hz. 3 Hz–10 6 Hz. By analyzing the dielectric response parameters of materials at different frequencies, such as dielectric constant and dielectric loss factor, a precise mapping relationship between these parameters and the current moisture content of the material can be established.

[0024] (1) Selection and measurement of dielectric response parameters In 10 3 Hz to 10 6 A sweep frequency dielectric spectrum of the freeze-dried material was measured over a wide frequency range of Hz, and the real part of the dielectric constant at each frequency point was recorded. Dielectric loss factor and loss tangent The real part of the dielectric constant is... Dielectric loss factor reflects the ability of a material to store electrical energy. Both reflect the loss characteristics of materials in converting electrical energy into heat energy, and are closely related to the internal moisture content and the state of moisture (free water, bound water) of the material.

[0025] (2) Characteristic frequency calibration Within the specified wide frequency range, the dielectric loss spectra of the same material were measured using standard samples with different known moisture contents (it is recommended that there be no fewer than 5 levels of moisture content gradient, covering 0% to the initial moisture content). The frequency points with the highest sensitivity of the dielectric loss factor to changes in moisture content and the least interference from ionic conductivity were selected as characteristic frequencies. The specific criterion is: at that frequency point, the change in dielectric loss factor caused by a 1% change in water content. At its maximum, the temperature drift coefficient of the real part of the dielectric constant is also reached. Less than a preset threshold (typically 0.5 / °C). For most biological and food materials, the characteristic frequency... Usually located at 10 4 Hz to 10 5 Hz range.

[0026] (3) Calibration function fitting At the characteristic frequency Below, the measured dielectric loss factor of each standard sample is used. Using the x-axis as the horizontal axis and the corresponding known moisture content w as the y-axis, a least-squares fit is performed to establish a calibration function, i.e., the mapping relationship between the dielectric response parameter and the material moisture content:

[0027] In the formula, The calibration coefficients, which are related to the material type, are determined through fitting. The real part of the dielectric constant is introduced in this process. As the second independent variable, it is used to correct for the influence of differences in material density and pore structure on the dielectric response; the quadratic term Nonlinear characteristics used to fit the dielectric response in high water content regions.

[0028] (4) Temperature compensation correction Since the dielectric response parameters are temperature-dependent, the above calibration function needs to be performed at a reference temperature. (Usually established at 20℃ or 25℃). In actual measurements, if the material temperature... Deviation Temperature compensation is required for the dielectric loss factor.

[0029] in, This is the temperature correction factor for the dielectric loss factor, obtained by measuring the dielectric loss factor of the same moisture content sample at different temperatures. Its value typically ranges from 0.01°C to 0.03°C. The compensated value will then be... Substituting the values ​​into the calibration function yields the temperature-corrected moisture content w.

[0030] (5) Multi-frequency cross-validation To improve the reliability of the mapping relationship, in addition to the characteristic frequency External auxiliary frequency points (usually taken) = 10 or = At point / 10), an auxiliary calibration function is established simultaneously. The moisture content calculation results from the characteristic frequency and the auxiliary frequency are cross-validated. If the deviation exceeds 5%, a recalibration prompt is triggered; if the deviation is within 5%, the weighted average is taken as the final moisture content.

[0031] (6) Collapse temperature correlation After obtaining the moisture content w, a correlation database between moisture content and collapse temperature is further established: the glass transition temperature of the material at different moisture contents is determined by differential scanning calorimetry (DSC) or thermomechanical analysis (TMA). The fitting yielded The function allows you to determine the collapse temperature limit under the current material condition by substituting the real-time measured moisture content *w* into this function. (usually taken) ).

[0032] Based on this mapping relationship, two key process parameters of the material to be freeze-dried can be determined in advance: Collapse temperature limit: the highest temperature at which a material can maintain its porous structure without collapsing during the drying process.

[0033] Safe heating rate is the maximum permissible heating rate for transitioning from low to high temperature, provided that the material temperature does not exceed the collapse temperature.

[0034] S2: The material to be freeze-dried is placed in a freeze-drying chamber with multiple independent temperature control zones, and a directional temperature gradient field is established in each temperature control zone to induce ice crystals in the material to grow in a predetermined direction.

[0035] The material to be freeze-dried is placed in a freeze-drying chamber with multiple independent temperature-controlled zones. In this embodiment, the freeze-drying chamber has at least three independent temperature-controlled zones. By setting different target temperatures in each temperature-controlled zone, for example, setting the top temperature-controlled zone to -50°C, the bottom temperature-controlled zone to -30°C, and the middle zone to a transition temperature, a top-down directional temperature gradient field is established throughout the freeze-drying chamber. This gradient field induces ice crystals inside the material to be freeze-dried to grow directionally along a preset vertical direction (from the low-temperature zone to the high-temperature zone). This directionally grown ice crystal structure can form ordered porous channels during subsequent sublimation, which is conducive to the escape of water vapor, thereby improving drying efficiency and product rehydration properties.

[0036] S3: Real-time acquisition of the real part change trend of the radio frequency impedance of each temperature control zone. When the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and a pulsed differential pressure cycle is performed on the temperature control zone to enhance mass transfer.

[0037] During the sublimation drying stage, the system acquires the real part change trend of the radio frequency impedance in each independent temperature control zone in real time. The real part of the radio frequency impedance is closely related to the local moisture content of the material to be freeze-dried and the position of the sublimation front. When the rate of change of the real part of the radio frequency impedance (i.e., the amount of impedance change per unit time) in any temperature control zone decays to a preset approximate value, and the measured material temperature in that zone is still lower than the collapse temperature limit determined in step S1, the system determines that the free ice in that zone has basically sublimated and has entered the turning point of analytical drying.

[0038] At this point, the system automatically switches the heating mode of the temperature-controlled zone from a high-power sublimation heating mode (primarily providing latent heat of sublimation) to a relatively mild desorption heating mode (primarily providing desorption heat). Simultaneously, a pulsating differential pressure cycle is initiated in the temperature-controlled zone to enhance mass transfer. The pulsating differential pressure cycle executes three stages sequentially: Vacuum depressurization stage: Used to quickly reduce the pressure inside the freeze-drying chamber.

[0039] Pressure maintenance phase: The pressure inside the freeze-drying chamber is stabilized between 10 Pa and 30 Pa for about 90 seconds to promote the desorption of bound water by utilizing the low-pressure environment.

[0040] Instantaneous pressure boost and depressurization phase: By introducing a dry inert gas (such as nitrogen), the pressure inside the chamber jumps to 50 Pa to 80 Pa in a short time (about 30 seconds), followed by rapid depressurization. This pressure pulse can effectively break the concentration boundary layer on the material surface, carrying away the desorbed water vapor from the material and greatly enhancing the mass transfer process. The cycle of the entire pulsation is preferably 120 seconds.

[0041] S4: Real-time acquisition of material temperature in each temperature control zone, dynamic comparison of the material temperature with the expected temperature curve generated based on the material thermophysical property model, and adaptive adjustment of heating power and / or adjustment of process parameters of the pulsating differential pressure cycle when the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit. Throughout the drying process, the system continuously collects the material temperature in each temperature control zone in real time and dynamically compares it with an expected temperature curve generated based on a material thermophysical property model.

[0042] The method for generating the expected temperature curve based on the material's thermal property model is as follows: (1) Obtain the thermophysical parameters of the material to be freeze-dried at different moisture contents, and establish a correlation model between the thermophysical parameters and the moisture content: Determine the density of the freeze-dried material in its oven-dry state. Specific heat capacity and thermal conductivity Simultaneously, the equivalent heat capacity at different moisture contents w was determined. With equivalent thermal conductivity Establish associations:

[0043]

[0044] in The material property coefficient w is obtained through experimental calibration. It is obtained in real time from the aforementioned dielectric spectrum mapping relationship or set according to the initial moisture content.

[0045] 2) Using the initial moisture content, target moisture content, collapse temperature limit, safe heating rate, and chamber pressure as model boundary conditions, a one-dimensional unsteady heat transfer model is established along the material thickness direction, and heat transfer boundary conditions are set between the material and the shelf and the chamber gas. Set drying process parameters: Initial moisture content Target moisture content Collapse temperature limit Safe heating rate and chamber pressure As a boundary condition input to the model, the safe heating rate is one of the following: Based on the current material temperature and The temperature margin between chambers is determined by a piecewise function; chamber pressure The sequence is given according to the pulsating differential pressure cycle setting.

[0046] Establish a one-dimensional unsteady heat transfer model: The material is discretized into several computational layers along the thickness direction, each layer having a thickness of... Taking the shelf contact surface as... =0, the top surface of the material is x=L. Establish the energy conservation equation for each computational layer:

[0047] In the formula, The latent heat of sublimation of ice; w / t represents the rate of change in moisture content, given by the sublimation front propagation model or the drying rate curve calibrated experimentally.

[0048] Boundary conditions: The bottom surface of the material (x=0) is in contact with the shelf, according to the third type of boundary condition:

[0049] The top surface of the material (x=L) is in contact with the gas in the drying chamber:

[0050] Initial conditions: .

[0051] 3) The corresponding thermophysical parameters are dynamically updated based on the moisture content and temperature of each layer of the material, and the temperature distribution of the material along the thickness direction at each moment is obtained iteratively using a numerical solution method.

[0052] The above equations are solved discretly using the finite difference method. At each time step... Inside: Update the data for this layer based on the current moisture content w and temperature T of each layer. ; Based on safe heating rate Calculate the target temperature of the shelf = T0+ ·t; By solving the system of discrete algebraic equations simultaneously, the temperature distribution of each layer at the next time step can be obtained. .

[0053] 4) Extract the temperature values ​​at corresponding locations in each temperature control zone and process them to form the expected temperature curve of each temperature control zone over time.

[0054] Extract the temperature value at the corresponding location in each temperature control zone as the expected temperature at that moment. .

[0055] Iterative calculations were performed along the entire drying time to obtain discrete sequences of temperature variations over time at each temperature control zone. After smoothing, a continuous expected temperature curve was formed. .

[0056] Furthermore, it also includes a dynamic correction process: During the drying process, the system corrects the expected temperature curve online based on the deviation between the moisture content w(t) measured in real time by dielectric spectrum and the model prediction value: when the measured moisture content is lower than the model prediction, it indicates that the drying rate is higher than expected, and the expected heating rate in subsequent periods is increased accordingly; otherwise, the expected heating rate is reduced so that the curve always fits the actual drying state of the material.

[0057] The expected temperature curve is the optimal heating path calculated based on the material's heat capacity, thermal conductivity, initial moisture content, and the set drying process parameters.

[0058] When the deviation between the actual material temperature and the expected temperature curve exceeds the preset safety tolerance (e.g., ±2°C), or when the material temperature begins to approach the collapse temperature limit determined in step S1, the system will immediately trigger an adaptive adjustment mechanism. This mechanism will: The heating power of the corresponding temperature control zone is automatically reduced, typically by 10% to 30% of the current power.

[0059] And / or adjust the process parameters of the pulsating differential pressure cycle, such as increasing the frequency of the variable frequency vacuum pump by 5% to 15% of the current frequency, to accelerate heat dissipation and moisture removal and prevent the material from overheating and collapsing.

[0060] S5: Apply a low-temperature plasma field to the cold trap region of the freeze-drying chamber to reduce the partial pressure of water vapor on the surface of the cold trap and promote the removal of bound water inside the material.

[0061] During the desorption and drying stage, especially to remove stubborn bound water, a low-temperature plasma field is applied to the cold trap region of the freeze-drying chamber. This plasma field is applied intermittently using dielectric barrier discharge, with a discharge power of 5 W to 20 W and a duty cycle of 20%. The low-temperature plasma contains a large number of high-energy electrons and active free radicals, which act on the surface of the cold trap, effectively reducing the water vapor partial pressure on the surface of the cold trap. This increases the water vapor partial pressure difference between the cold trap and the material, significantly promoting the removal efficiency of bound water inside the material.

[0062] S6: When the dielectric response parameters are stable and the water vapor partial pressure in the freeze-drying chamber is lower than the preset threshold, the freeze-drying process ends.

[0063] When the dielectric response parameters monitored by the system stabilize (indicating that the moisture content of the material no longer changes significantly) and the water vapor partial pressure in the freeze-drying chamber is lower than a preset threshold, the system determines that the freeze-drying process has ended. This preset threshold can be defined by a mass spectrometer, for example, the water vapor partial pressure corresponding to a water peak intensity in the chamber that is lower than three standard deviations of the background noise.

[0064] Example 2 This embodiment provides an adaptive freeze-drying system for performing the above-described method. The system includes the following modules: Mapping Relationship Establishment Module: This module is used to perform the function of step S1. It includes a broadband dielectric spectrum analyzer for measuring the dielectric properties of materials and establishing a mapping relationship between dielectric parameters and moisture content and collapse temperature.

[0065] The pretreatment homogenization module performs the functions of step S2. At its core is a freeze-drying chamber with multiple independent temperature-controlled zones. Each temperature-controlled zone is equipped with an array of dielectric-thermal conductivity inductive heating plates. These heating plates integrate radio frequency impedance sensors and thin-film heat flux sensors. The radio frequency impedance sensors operate in a 1–100 MHz sweep mode to invert the local moisture content of the material and the sublimation front position in real time; the thin-film heat flux sensors monitor the latent heat flux of sublimation, providing input data for the thermophysical property model. In addition, the module may also include an ultrasonic atomization pre-freezing unit and a directional temperature gradient field generator to form a radially ordered, axially gradient-controllable ice crystal framework during the pre-freezing stage.

[0066] The pulsed differential pressure mass transfer drive module is used to execute the function in step S3. This module is connected to the exhaust port of the freeze-drying chamber and mainly includes a main evacuation pipeline, a variable frequency vacuum pump, and a smart butterfly valve. One end of the main evacuation pipeline is connected to the freeze-drying chamber, and the other end is connected to the variable frequency vacuum pump. The smart butterfly valve is installed on the main evacuation pipeline and has a built-in angular displacement sensor and pressure feedforward controller. It can accurately and quickly adjust the valve opening according to control commands, thereby realizing the aforementioned complex pressure cycles such as evacuation, pressure holding, and instantaneous pressure increase. This module is responsible for switching the heating mode and executing the pulsed differential pressure cycle at the end of the sublimation drying process.

[0067] The adaptive adjustment module performs the function of step S4. It is communicatively connected to the RF impedance sensor, thin-film heat flow sensor, pulsating differential pressure mass transfer drive unit, plasma-activated cold trap module, and each zone heating plate. This module receives temperature sensor data and RF impedance data from each temperature control zone and compares them with the internally stored material thermophysical property model and expected temperature curve. It has built-in zone threshold judgment logic; once an anomaly is detected, it immediately issues a command to automatically reduce the heating power of the corresponding zone heating plate and / or adjust the frequency of the variable frequency vacuum pump, achieving closed-loop adaptive control of the drying process.

[0068] The plasma-activated cold trap module performs the function of step S5. This module is located on the surface of the cold trap coil in the freeze-drying chamber and is loaded with dielectric barrier discharge electrodes. The control system intermittently excites the DBD electrodes according to set parameters (5–20 W power, 20% duty cycle) to generate low-temperature plasma and activate the cold trap surface.

[0069] The judgment module is used to execute the function of step S6. This module comprehensively analyzes the dielectric response data from the mapping relationship establishment module and the water vapor partial pressure data from the sensors in the freeze-drying chamber. When both meet the preset endpoint conditions, it issues a command to stop drying.

[0070] Preferably, the system includes a tail gas heat recovery and solvent capture module, which is equipped with a stepped condenser and an activated carbon-zeolite gel composite adsorption layer arranged sequentially along the airflow direction. The stepped condenser can recover heat from the tail gas and initially capture condensable solvents, while the composite adsorption layer can deeply purify the tail gas, ensuring that emissions meet standards and recovering valuable solvents.

[0071] Example 3 Taking Zn0.5Cd0.5S nanosheet photocatalyst as an example, the adaptive freeze-drying and solvothermal method are as follows: The Zn0.5Cd0.5S wet gel prepared by reacting with a mixed solvent of ethylenediamine and deionized water at 180℃ for 24 h was dispersed in anhydrous ethanol after centrifugation and washing. The solid content was about 8 wt%, and the initial solvent water content was about 85 wt% (containing the ethanol / water mixed solvent).

[0072] S1: Dielectric spectrum calibration and initial parameter mapping The above wet gel slurry was subjected to a frequency of 10. 3 -10 6 Broadband dielectric spectroscopy was performed within the Hz range. Since Zn0.5Cd0.5S is a polar semiconductor, its dielectric loss factor is sensitive to adsorbed water molecules. The initial peak dielectric loss factor corresponds to a water content of approximately 85 wt%, and a dielectric loss factor-water content correlation curve was obtained. The collapse temperature of the gel framework was determined using thermogravimetric-differential scanning calorimetry (TGC-DC-DCS). for The safe heating rate is 0.5℃ / min, set at 18℃. The calibration parameters are then written into the adaptive control module.

[0073] S2: Partial Pre-freezing and Directed Ice Crystal Growth The slurry was coated onto a 6 mm thick PTFE freeze-drying tray and placed inside a multi-chamber adaptive freeze-drying chamber. Three independent temperature control zones were set: top zone... 50℃, Central Region 38℃, bottom area At 25℃, a top-down directional temperature gradient was established. The ultrasonic atomization pre-freezing unit was activated, allowing the material to form a radially ordered ice crystal framework with a controllable axial gradient within 25 minutes. The ice crystals grew directionally along the heat flow direction, establishing a vertical mass transfer channel for subsequent sublimation. After pre-freezing, the temperature inside the chamber stabilized at 25℃. 42℃.

[0074] S3: Adaptive Sublimation of Pulsating Pressure Difference The main freeze-drying stage begins. The adaptive control module reads the real data from the RF impedance sensors (1–100MHz sweep) of each zone at 30-second intervals. The bottom zone appears first. Approaching zero (measured rate of change << 0.05 min) - ¹), and the material temperature measured by the thin-film heat flow sensor in this area. 20℃ (below the collapse temperature limit) The system automatically adjusts the temperature of the bottom heating plate from sublimation drying mode. Switch to the desorption and drying mode at 25℃. The temperature was increased to 8℃ to remove hydrogen-bonded water and residual ethanol from the Zn0.5Cd0.5S surface, and the frequency of the variable frequency vacuum pump was simultaneously increased by 10% to enhance the mass transfer driving force. Meanwhile, the pulsating pressure difference mass transfer driving unit executed a pulsating cycle with a period of 120 s: the pressure holding phase maintained the chamber pressure at 15 Pa for 90 s; the pressure relief phase instantaneously introduced dry argon gas to 60 Pa via a smart butterfly valve for 30 s. The periodic pressure difference fluctuations broke the stagnant vapor layer within the gel channels, promoting the diffusion of ethanol-water azeotrope from the mesopores.

[0075] S4: Safety threshold closed-loop correction The measured material temperature in the central region was 4.5 hours after the main drying process began. 16.5℃, while the expected temperature curve based on the thermophysical property model is 15℃, deviation is The temperature was 1.5℃, which did not exceed the preset threshold of ±2℃, and the system maintained the current parameters. At the 6th hour, the measured temperature in the top area rose to... 16 ℃, approaching the collapse temperature At 18℃ (with a margin of only 2℃), the adaptive control module triggers a safety threshold closed-loop correction: the heating power in this zone is reduced by 20%, the pressure holding time in the pulsation cycle is shortened from 90 s to 75 s to accelerate mass transfer cooling, and the vacuum pump frequency is increased by 5%, so that the temperature in this zone drops back to normal within 10 minutes. 19℃, to avoid the nanosheets from stacking due to localized remelting.

[0076] S5: Plasma-assisted desorption and drying During the later stages of desorption and drying (when the water content, as determined by dielectric spectroscopy, drops to approximately 5 wt%), the plasma-activated cold trap is activated, and low-temperature plasma is intermittently applied to the dielectric barrier discharge electrode at a power of 12 W and a duty cycle of 20%. The partial pressures of water vapor and ethanol vapor in the freeze-drying chamber decrease from 6 Pa to 2 Pa, promoting the removal of solvents bound by hydrogen bonds within the Zn0.5Cd0.5S mesopores. Simultaneously, the plasma decomposes trace amounts of residual ethylenediamine in situ, preventing nitrogen-containing organic matter from contaminating the active sites on the catalyst surface. After recovering ethanol (recovery rate >88%), the exhaust gas is further purified by an activated carbon-zeolite gel composite adsorption layer to remove residual VOCs.

[0077] S6: Intelligent Discharge When the dielectric loss factor fluctuates by less than 0.3% for 20 consecutive minutes, and the intensity of the water peak and ethanol peak measured by the residual gas analyzer is less than 3 times the standard deviation of the background noise, the adaptive control module determines that the endpoint has been reached, automatically stops heating and breaks the vacuum to discharge the material.

[0078] Effect Comparison Compared to conventional oven drying (60℃, 12h), the Zn0.5Cd0.5S obtained in this embodiment has a BET specific surface area of ​​142 m² / g (compared to only 68 m² / g by oven drying), a pore volume of 0.38 cm³ / g (compared to only 0.15 cm³ / g by oven drying), and an average pore size that remains at 9 nm after changing from 12 nm, without significant pore collapse. In the visible light-driven CO2 reduction reaction (using TEOA as a sacrificial agent), the CO generation rate is 28.6 μmol·g. - ¹·h - ¹, compared to oven-dried samples (14.2 μmol·g⁻¹) - ¹·h - ¹) The 101% improvement is attributed to the freeze-drying process maintaining highly exposed crystal planes and three-dimensional porous mass transfer channels.

[0079] Example 4 The adaptive freeze-drying of CeO2 / Co3O4 S-type heterojunction photocatalyst involved preparing a CeO2 / Co3O4 composite wet gel (CeO2 loading 3 wt%, cerium nitrate as the cerium source, and cobalt hydroxide as the Co3O4 precursor) using the in-situ calcination precursor method. After washing with deionized water, the gel was dispersed in anhydrous ethanol, with a solid content of approximately 10 wt% and an initial water content of approximately 88 wt%. This heterojunction is extremely sensitive to interfacial structure; conventional drying methods easily lead to the detachment or migration and aggregation of CeO2 nanoparticles from the Co3O4 surface.

[0080] S1: Dielectric spectrum calibration and initial parameter mapping Broadband dielectric spectroscopy was performed on the composite gel. Due to the significant difference in dielectric constants between CeO2 and Co3O4, the dielectric spectrum exhibited a bimodal characteristic, corresponding to adsorbed water in the Co3O4 matrix and hydroxyl water on the CeO2 surface, respectively. The collapse temperature of the composite gel was determined after comprehensive calibration. for At 20℃, the upper limit of the safe heating rate is 0.4℃ / min.

[0081] S2: Partial Pre-freezing and Directed Ice Crystal Growth The gel was coated onto a tray to a thickness of 5 mm and placed inside a four-zone freeze-drying chamber. Temperature gradient was set: top. 50℃, upper middle 42℃, lower middle part 35℃, bottom At 25℃, ice crystals are induced to grow directionally along the direction perpendicular to the heat flow, forming a through-type sublimation channel to reduce the risk of shear damage to the heterojunction interface under capillary force.

[0082] S3: Adaptive Sublimation of Pulsating Pressure Difference After the main freeze-drying stage starts, the radio frequency impedance sensors in each zone monitor the process in real time. The lower-middle zone reaches the sublimation endpoint first. <<0.03 min - ¹, material temperature At 22℃, the adaptive control module switches this area to the analytical drying mode. The temperature is set at 10℃ to remove hydrogen-bonded water at the CeO2 / Co3O4 interface. The other three regions maintain sublimation mode. The pulsating pressure difference mass transfer drive unit performs a 120-second cycle of holding pressure at 18 Pa and releasing pressure to 55 Pa (dry argon). The periodic pressure difference thrust effectively strips away the solvent trapped between the Co3O4 nanosheets, preventing CeO2 particles from detaching from the interface due to liquid bridging forces during the drying process.

[0083] S4: Safety threshold closed-loop correction The nanocomposite gel has a low thermal conductivity. At the 4th hour, the latent heat flux measured by the thin-film heat flux sensor in the upper and middle regions suddenly increased, corresponding to the measured material temperature. 17℃, approaching the collapse temperature At 20°C, and with an abnormally enhanced unfrozen water signal in the dielectric spectrum of this region, it was indicated that local collapse might have led to CeO2 particles being embedded within the Co3O4 matrix, reducing the exposed interface. The adaptive control module immediately reduced the heating power in this region by 25%, shortened the holding time from 90 s to 80 s to enhance mass transfer cooling, and increased the vacuum pump frequency by 12%, causing the temperature in this region to drop back to normal within 8 minutes. At 21℃, the signal from unfrozen water attenuates, and the risk to the interface structure is eliminated.

[0084] S5: Plasma-assisted desorption and drying During the later stages of the drying process, plasma activation of the cold trap was initiated, with a power of 15W and a duty cycle of 20%. The low-temperature plasma reduced the solvent partial pressure on the cold trap surface and suppressed back diffusion. Simultaneously, it decomposed trace amounts of residual nitrate (from the cerium nitrate precursor) in situ, preventing nitrogen species from occupying active sites at the heterojunction interface.

[0085] S6: Intelligent Discharge The dielectric loss factor remained stable for 20 minutes, and the mass spectrometry peaks for water and NO were also stable. x If the relevant peak is below the threshold, the freeze-drying process will automatically end.

[0086] Effect Comparison Compared to traditional vacuum oven drying (80℃, vacuum degree) Compared to the previous method (0.09 MPa, 10 h), the total processing time in this embodiment was shortened to 7.5 h. Transmission electron microscopy showed that CeO2 nanoparticles (approximately 5 nm in diameter) were uniformly anchored on the surface of Co3O4 nanosheets without significant aggregation or detachment; X-ray photoelectron spectroscopy confirmed that the Ce–O–Co interfacial bonds remained intact. In the photocatalytic nitrogen fixation reaction (visible light, N2 / H2O system), the NH3 formation rate was 42.3 μmol·g⁻¹. - ¹·h - ¹, compared to traditionally dried samples (19.8 μmol·g) - ¹·h - ¹) The 114% improvement is attributed to the effective maintenance of the charge transfer channels at the S-type heterojunction interface by adaptive freeze drying.

[0087] Example 5 The adaptive freeze-drying of Bi cluster-confined Zn0.5Cd0.5S photocatalyst was carried out using Bi cluster-supported Zn0.5Cd0.5S colloid (Bi loading 0.5 at%, bismuth nitrate pentahydrate as bismuth source, thiol as stabilizer) prepared by a two-step solvothermal reduction method. The solid content was about 6 wt%, the initial water content was about 92 wt%, and it contained trace amounts of thiol dispersant (about 800 ppm) and ethanol.

[0088] S1: Dielectric spectrum calibration and initial parameter mapping Broadband dielectric spectroscopy was performed on the colloid. The introduction of Bi clusters enhanced the nonlinearity of the dielectric response, and the collapse temperature was measured. for The safe heating rate is 15℃ (lower than that of pure Zn0.5Cd0.5S, attributed to the thiol plasticizing effect), with an upper limit of 0.3℃ / min.

[0089] S2: Partial Pre-freezing and Directed Ice Crystal Growth The colloid was injected into a cylindrical freeze-drying mold, 15 mm in diameter and 10 mm in height, and placed inside a three-zone freeze-drying chamber. The top was then set. 50℃, Central 35℃, bottom A temperature gradient of 20°C induces the directional growth of ice crystals from bottom to top. During the ice crystal growth process, local confinement and exclusion effects are generated on Bi clusters, causing Bi clusters (approximately 1–2 nm in size) to be pre-enriched in the interstitial spaces of the ice crystals, providing a thermodynamic driving force for the formation of lattice-confined or surface-anchored structures after freeze-drying.

[0090] S3: Adaptive Sublimation of Pulsating Pressure Difference During the main freeze-drying stage, the central region was the first to complete sublimation. Approaching zero, material temperature 17℃), automatically switch to desorption drying mode ( 8℃). The pulsating cycle was set to maintain pressure at 22 Pa (85 s) and release pressure to 65 Pa (35 s, dry argon). The pressure fluctuation promoted the removal of the thiol-ethanol-water ternary system from the Zn0.5Cd0.5S interlayer and around the Bi clusters, avoiding the poisoning of catalytic sites by thiol residues during the drying process.

[0091] S4: Safety threshold closed-loop correction At the 5th hour, the measured material temperature in the bottom zone was... 13℃, approaching the collapse temperature The temperature in this region was 15℃, and an abnormal peak appeared in the imaginary part of the radio frequency impedance, indicating that the thiol-water complex was not completely removed. The adaptive control module triggered a correction: the heating power in this region was reduced by 30%, the pressure holding time was shortened to 70 seconds, the vacuum pump frequency was increased by 15%, and the plasma activation cold trap was activated earlier (power 10 W) to reduce the partial pressure of organic vapors inside the chamber. After correction, the temperature in this region returned to normal. At 16℃, the signal of the thiol complex decays.

[0092] S5: Plasma-assisted desorption and drying During the desorption and drying stage, the plasma-activated cold trap power is maintained at 10 W and the duty cycle at 20%. Low-temperature plasma effectively decomposes thiols and trace amounts of bismuth nitrate decomposition residues, preventing sulfur species from occupying coordination sites on the Bi cluster surface. After the exhaust gas undergoes staged condensation to recover ethanol, sulfur-containing volatiles are captured by a zeolite gel adsorption layer.

[0093] S6: Intelligent Discharge With a stable dielectric loss factor and organic sulfur peak below the threshold, the material is automatically discharged.

[0094] Effect Comparison Compared with traditional freeze drying (continuous vacuum 15Pa, fixed plate temperature) Compared to the previous method (20℃, total duration 16h), the total duration of this embodiment was shortened to 10h. Aberration-corrected transmission electron microscopy showed that Bi clusters were uniformly distributed at the sub-nanometer scale on the surface and between layers of Zn0.5Cd0.5S, without the Ostwald ripening of Bi clusters caused by slow solvent evaporation in traditional freeze-drying (where cluster size increases to 4–6 nm). X-ray photoelectron spectroscopy confirmed the retention of Bi–S coordination bonds. In the visible light-driven CO2 reduction reaction, the CO selectivity was 78% (compared to 62% in traditional freeze-drying), and the total carbon product formation rate was 35.4 μmol·g. - ¹·h - ¹, which improves upon traditional freeze-drying by 67%, is attributed to the effective suppression of photogenerated carrier recombination by the Bi cluster confinement structure.

[0095] Example 6 Adaptive freeze-drying of TiO2 mesoporous photocatalytic support materials TiO2 wet gel prepared by sol-gel method (tetrabutyl titanate as titanium source, Pluronic F127 as template agent) was aged for 48 h and then replaced with ethanol. The solid content was about 5 wt%, and the initial solvent water content was about 80 wt% (containing ethanol / water and trace amounts of butanol).

[0096] S1: Dielectric spectrum calibration and initial parameter mapping Broadband dielectric spectroscopy was performed on the wet gel. Due to the presence of the F127 template agent, the dielectric spectrum was within 10... 4 A template relaxation peak appears at Hz, which can be used to distinguish between free solvent and template-bound solvent. The collapse temperature is then calibrated. for At 22℃, the upper limit of the safe heating rate is 0.6℃ / min.

[0097] S2: Partial Pre-freezing and Directed Ice Crystal Growth The gel was placed in a freeze-drying chamber to a thickness of 12 mm, and a four-zone temperature gradient was set: top... 50℃, upper part 40℃, lower part 32 ℃, bottom 25℃. Directional pre-freezing causes ice crystals to grow in a vertical direction, forming an ordered macroporous template. After subsequent sublimation, F127 is removed by calcination, yielding highly ordered mesoporous-macroporous hierarchical TiO2.

[0098] S3: Adaptive Sublimation of Pulsating Pressure Difference During the main freeze-drying stage, the bottom region is the first to complete sublimation and switch to desorption mode. The pulsed pressure differential drive unit performs a cycle of holding pressure at 12 Pa and releasing pressure to 50 Pa. Due to the abundant pores in the TiO2 gel (pore size distribution 2–50 nm), the pulsed pressure differential effectively promotes the removal of butanol-ethanol-water azeotrope from the mesopores, avoiding template agent residue and blockage within the pores.

[0099] S4: Safety threshold closed-loop correction At 7 hours, the measured temperature in the lower region 19℃, approaching the collapse temperature At 22℃, the adaptive control module reduces the power in this area by 20%, shortens the pressure holding time, and maintains the stability of the channel structure.

[0100] S5: Plasma-assisted desorption and drying In the later stages of analysis, the plasma cold trap (power 8 W) is activated to decompose trace amounts of butanol and F127 thermal decomposition intermediates, and to purify the surface of the cold trap.

[0101] S6: Intelligent Discharge After the dielectric spectrum stabilizes, the material is discharged, and the resulting freeze-dried body is calcined at 550℃ for 2 hours to remove the template agent.

[0102] Effect Comparison Compared to traditional oven drying (80℃, 24h), the TiO2 obtained in this example, after calcination, has a BET specific surface area of ​​286 m² / g (compared to only 142 m² / g after oven drying), a pore volume of 0.52 cm³ / g, and maintains a highly ordered mesoporous-macroporous hierarchical structure. In the photocatalytic degradation of Rhodamine B, the first-order kinetic constant is 0.045 min⁻¹. - ¹, compared to oven-dried samples (0.021 min) - ¹) The 114% increase is attributed to the freeze-drying-calcination synergy that maintains a high specific surface area and interconnected channels.

[0103] Example 7 Performance verification of the exhaust gas heat recovery and solvent capture module in catalyst preparation (based on Example 3) During the freeze-drying process in Example 3, the exhaust gas heat recovery and solvent capture modules were monitored simultaneously. The gas discharged from the vacuum pump first passed through a stepped condenser (first stage). 5℃, Level 2 At 25℃, the ethanol capture rate was measured to be 90.5%, and the recovered ethanol can be directly reused in the catalyst washing section. Residual gas enters the activated carbon-zeolite gel composite adsorption layer, with an outlet VOCs concentration << 4 mg / m³, meeting laboratory and industrial environmental emission requirements. The cooling energy recovered by the cascade condenser is used in the pre-cooling section of the pretreatment homogenization module via a heat exchanger, reducing the energy consumption per batch of pre-freezing by approximately 16%. After 15 batches of continuous operation, the zeolite gel composite adsorption layer undergoes thermal desorption regeneration at 150℃, achieving a 93% adsorption capacity recovery rate, and can be recycled for subsequent catalyst freeze-drying processes.

[0104] As can be seen from the above embodiments, this invention addresses the core pain points of photocatalytic materials, heterojunction composite catalysts, and supported nanocatalysts during the drying process, such as pore retention, interface stability, and solvent residue control. Through the synergistic effect of dielectric-thermal conductivity inductive real-time inversion, zoned adaptive mode switching, pulsed pressure difference mass transfer drive, and plasma-activated cold trap, it achieves efficient, low-loss, and low-residue freeze-drying of catalyst precursors, significantly improving the specific surface area, active site exposure, and photocatalytic reaction performance of the catalyst. It has broad industrial application prospects in the fields of environmental photocatalysis, energy catalysis, and fine chemical catalyst preparation.

[0105] In summary, this invention utilizes the mature, simple, reproducible, and highly operable electrospinning thermal and high-temperature selenization methods to prepare a carbon fiber composite battery material, which can be used as a negative electrode material for sodium-ion batteries. The structure of this material, through the interconnection of carbon fibers and the construction of heterogeneous structures, alleviates the problem of nanosheet agglomeration while providing more active sites for electrode reactions. The optimized interfacial electric field promotes electron / ion transport, significantly improving the rate performance and cycle stability of sodium-ion batteries. It may also provide technical reference for other types of batteries such as lithium-ion and potassium-ion batteries, possessing high application value and market potential.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An adaptive freeze-drying method, characterized in that, Includes the following steps: Broadband dielectric spectrum was measured on the material to be freeze-dried to establish a mapping relationship between dielectric response parameters and material moisture content, and the collapse temperature limit and safe heating rate of the material to be freeze-dried were determined based on the mapping relationship. The material to be freeze-dried is placed in a freeze-drying chamber with multiple independent temperature control zones. A directional temperature gradient field is established in each temperature control zone to induce ice crystals in the material to grow in a predetermined direction. The real part change trend of the radio frequency impedance of each temperature control zone is acquired in real time. When the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and a pulsed differential pressure cycle is performed on the temperature control zone to enhance mass transfer. The material temperature in each temperature control zone is collected in real time, and the material temperature is dynamically compared with the expected temperature curve generated based on the material thermal property model. When the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the heating power of the corresponding temperature control zone is adaptively reduced and / or the process parameters of the pulsating differential pressure cycle are adjusted. Applying a low-temperature plasma field to the cold trap region of the freeze-drying chamber reduces the partial pressure of water vapor on the surface of the cold trap, promoting the removal of bound water from the material. The freeze-drying process ends when the dielectric response parameters are stable and the water vapor partial pressure in the freeze-drying chamber is lower than a preset threshold.

2. The adaptive freeze-drying method according to claim 1, characterized in that, In the step of performing broadband dielectric spectroscopy on the freeze-dried material, establishing a mapping relationship between the dielectric response parameters and the material moisture content, and determining the collapse temperature limit and safe heating rate of the material based on the mapping relationship, the established mapping relationship between the dielectric response parameters and the material moisture content is as follows: in, , For calibration coefficients related to material type, It is the dielectric loss factor. The characteristic frequency is denoted as .

3. The adaptive freeze-drying method according to claim 1, characterized in that, In the step of acquiring the real part change trend of the radio frequency impedance of each temperature control zone in real time, when the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and a pulsed pressure differential cycle is performed on the temperature control zone to enhance mass transfer. The pulsed pressure differential cycle includes a pumping and depressurization stage, a pressure holding stage, and an instantaneous pressure increase and depressurization stage executed in sequence.

4. The adaptive freeze-drying method according to claim 1, characterized in that, In the step of real-time acquisition of material temperature in each temperature control zone, dynamic comparison of the material temperature with the expected temperature curve generated based on the material thermal property model, and adaptive adjustment of the heating power of the corresponding temperature control zone and / or adjustment of the process parameters of the pulsating differential pressure cycle when the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the method for generating the expected temperature curve based on the material thermal property model is as follows: Obtain the thermophysical property parameters of the material to be freeze-dried at different moisture contents, and establish a correlation model between the thermophysical property parameters and the moisture content; Using initial moisture content, target moisture content, collapse temperature limit, safe heating rate and chamber pressure as model boundary conditions, a one-dimensional unsteady heat transfer model along the material thickness direction is established, and heat transfer boundary conditions between the material and the shelf and the chamber gas are set. The corresponding thermophysical parameters are dynamically updated based on the moisture content and temperature of each layer of the material, and the temperature distribution of the material along the thickness direction at each moment is obtained iteratively using a numerical solution method. Extract the temperature values ​​at corresponding locations in each temperature control zone, and process them to form the expected temperature curve of each temperature control zone over time.

5. The adaptive freeze-drying method according to claim 1, characterized in that, In the step of applying a low-temperature plasma field to the cold trap region of the freeze-drying chamber to reduce the partial pressure of water vapor on the surface of the cold trap and promote the removal of bound water inside the material, the low-temperature plasma field is applied intermittently using a dielectric barrier discharge method, with a discharge power of 5W to 20W and a duty cycle of 20%.

6. An adaptive freeze-drying system for performing the adaptive freeze-drying method as described in any one of claims 1 to 5, characterized in that, include: The mapping relationship establishment module is used to perform broadband dielectric spectrum determination on the freeze-dried material, establish a mapping relationship between dielectric response parameters and material moisture content, and determine the collapse temperature limit and safe heating rate of the material based on the mapping relationship. The pretreatment homogenization module is used to place the material into a freeze-drying chamber with multiple independent temperature control zones, establish a directional temperature gradient field in each temperature control zone, and induce ice crystals in the material to grow in a predetermined direction. The pulsed differential pressure mass transfer drive module is used to acquire the real part change trend of the radio frequency impedance of each temperature control zone in real time. When the rate of change of the real part of the radio frequency impedance of any temperature control zone decays to a preset approach value and the measured temperature of the material in the corresponding zone is lower than the collapse temperature limit, the heating mode of the temperature control zone is switched from sublimation heating mode to analytical heating mode, and the pulsed differential pressure cycle is performed on the temperature control zone to enhance mass transfer. An adaptive adjustment module is used to collect the material temperature of each temperature control zone in real time, and dynamically compare the material temperature with the expected temperature curve generated based on the material thermal property model. When the deviation exceeds the preset safety tolerance or the material temperature approaches the collapse temperature limit, the heating power of the corresponding temperature control zone is adaptively reduced and / or the process parameters of the pulsating differential pressure cycle are adjusted. The plasma-activated cold trap module is used to apply a low-temperature plasma field to the cold trap region of the freeze-drying chamber, reduce the water vapor partial pressure on the surface of the cold trap, and promote the removal of bound water from the material. The judgment module is used to end the freeze-drying process when the dielectric response parameters are stable and the water vapor partial pressure in the freeze-drying chamber is lower than a preset threshold.

7. The adaptive freeze-drying system according to claim 6, characterized in that, The freeze-drying chamber of the pretreatment homogenization module is equipped with at least three independent temperature control zones. Each temperature control zone is equipped with an array of dielectric-thermal conductivity inductive heating plates. The heating plates integrate radio frequency impedance sensors and thin-film heat flow sensors. The radio frequency impedance sensors are used to invert the local moisture content of the material and the sublimation front position in real time.

8. The adaptive freeze-drying system according to claim 7, characterized in that, The pulsed pressure differential mass transfer drive unit is connected to the freeze-drying chamber. The pulsed pressure differential mass transfer drive unit includes a main exhaust pipeline, one end of which is connected to the exhaust port of the freeze-drying chamber, and the other end is connected to the variable frequency vacuum pump. An intelligent butterfly valve is installed on the main exhaust pipeline. The intelligent butterfly valve has a built-in angular displacement sensor and a pressure feedforward controller for adjusting the valve opening.

9. The adaptive freeze-drying system according to claim 7, characterized in that, The plasma-activated cold trap module is disposed on the surface of the cold trap coil of the freeze-drying chamber and is loaded with dielectric barrier discharge electrodes.

10. An adaptive freeze-drying system according to claim 6, characterized in that, It also includes a tail gas heat recovery and solvent capture module, which includes a stepped condenser and an activated carbon-zeolite gel composite adsorption layer arranged sequentially along the airflow direction.

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