Supercritical drying production line process parameter intelligent control method and system

Abstract

The application discloses a supercritical drying production line process parameter intelligent control method and system, relates to the supercritical drying production line process parameter intelligent control field, and is used for realizing accurate control of the supercritical drying process and stable improvement of product quality, and comprises the following steps: obtaining distribution state information of a solvent in a gel in a reaction kettle; obtaining purity information of a circulating carbon dioxide fluid at a reaction kettle inlet and concentration information of the solvent in a fluid at a reaction kettle outlet; and comprehensively judging whether solvent replacement is completed according to the distribution state information, the purity information and the concentration information of the solvent in the fluid at the reaction kettle outlet.

Description

Technical Field

[0001] This invention relates to the field of intelligent control of process parameters in supercritical drying production lines, and particularly to an intelligent control method and system for process parameters in supercritical drying production lines. Background Technology

[0002] Traditional supercritical drying processes often struggle to precisely control the processing of wet gels containing multiple solvents, and when the purity of the carbon dioxide fluid used for extraction changes during recycling, leading to unstable product quality. Existing control methods primarily rely on macroscopic data, failing to detect microscopic solvent distribution within the gel and variations in the purity of the circulating fluid. This can result in misjudgments, causing product structural collapse and performance degradation. Summary of the Invention

[0003] This application discloses an intelligent control method and system for process parameters of a supercritical drying production line, which aims to solve the problem that traditional control methods are difficult to cope with when supercritical drying production lines process wet gels containing multiple solvents, and when the purity of the carbon dioxide fluid used for extraction changes during recycling. This can easily lead to unstable product quality and the "double blind spot" problem of the actual solvent distribution inside the gel and the changes in the state of the circulating fluid.

[0004] In a first aspect, this application discloses an intelligent control method for process parameters in a supercritical drying production line, comprising the following steps: Inside the reaction vessel, information on the distribution of the solvent within the gel is obtained; Obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the solvent concentration information of the fluid at the reactor outlet; By combining the distribution status information, the purity information, and the solvent concentration information in the fluid at the reactor outlet, it can be determined whether solvent replacement has been completed.

[0005] Optionally, information on the distribution of the solvent within the gel can be obtained, including: A microwave signal is applied to the gel, and the dielectric response characteristics after the interaction between the microwave signal and the gel are received; Based on dielectric response characteristics, information on the distribution state of solvent inside the gel is obtained.

[0006] Optionally, based on dielectric response characteristics, information on the distribution state of the solvent inside the gel can be obtained, including: The effective dielectric constant of the gel skeleton is estimated based on the dielectric response characteristics of microwave signals. Based on the effective dielectric constant, the background response caused by the gel skeleton in the dielectric response characteristics is subtracted; Based on the dielectric response characteristics after subtracting the background response, the distribution state information of the solvent inside the gel is obtained.

[0007] Optionally, a microwave signal is applied to the gel, and the dielectric response characteristics after the interaction between the microwave signal and the gel are received, including: A microwave signal is applied to the gel, and the original dielectric response characteristics after the interaction between the microwave signal and the gel are received; Obtain the morphological parameters of the gel; Based on the morphological parameters, the original dielectric response characteristics are corrected to obtain the dielectric response characteristics.

[0008] Optionally, obtain purity information of the circulating carbon dioxide fluid at the reactor inlet, including: An infrared beam is emitted through the circulating carbon dioxide fluid at the inlet of the reactor, and the transmitted spectral signal is received; Based on spectral signals, the purity information of the circulating carbon dioxide fluid at the reactor inlet is obtained.

[0009] Optionally, the spectral signal is a Raman scattering signal. Based on the spectral signal, the purity information of the circulating carbon dioxide fluid at the reactor inlet is obtained, including: Deconvolution processing is performed on the Raman scattering signal; Based on the characteristic peak positions and intensities of the Raman scattering signal after deconvolution processing, the type and concentration of residual solvent in the circulating carbon dioxide fluid at the reactor inlet are obtained to acquire purity information of the circulating carbon dioxide fluid at the reactor inlet.

[0010] Optionally, based on the comprehensive information on distribution status, purity, and solvent concentration in the fluid at the reactor outlet, it can be determined whether solvent replacement is complete, including: Based on the distribution status information, determine whether the solvent content in all regions inside the gel is lower than the preset solvent content threshold. Based on the purity information, determine whether the purity of the circulating carbon dioxide fluid is greater than the preset purity threshold; Based on the concentration information of the solvent in the fluid at the outlet of the reactor, determine whether the concentration of the solvent in the fluid at the outlet of the reactor is greater than a preset concentration threshold; Solvent replacement is considered complete when the solvent content in all regions inside the gel is lower than a preset solvent content threshold, the purity of the circulating carbon dioxide fluid is greater than a preset purity threshold, and the concentration of solvent in the fluid at the reactor outlet is less than a preset concentration threshold.

[0011] Optionally, the method also includes: When the solvent content in some areas inside the gel is higher than a preset solvent content threshold, and the rate of decrease in solvent content is less than the rate threshold, an auxiliary co-solvent is injected into the circulating carbon dioxide fluid, and pulsed microwave energy is emitted into the gel to promote solvent replacement.

[0012] Optionally, the injection rate of the auxiliary co-solvent satisfies the following relationship: V = (C_target F) / (rho_cosolvent); Where V is the injection rate of the auxiliary cosolvent, C_target is the mass concentration of the auxiliary cosolvent in the circulating carbon dioxide fluid, F is the flow rate of the circulating carbon dioxide fluid, and rho_cosolvent is the density of the auxiliary cosolvent.

[0013] Secondly, this application also discloses an intelligent control system for process parameters of a supercritical drying production line, the system comprising: The acquisition module is used to acquire information about the distribution of solvent inside the gel within the reactor. The spectral analysis module is used to obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the solvent concentration information in the fluid at the reactor outlet. The solvent replacement discrimination module is used to determine whether solvent replacement has been completed by comprehensively considering the distribution status information, purity information, and solvent concentration information in the fluid at the reactor outlet.

[0014] Beneficial effects This application discloses an intelligent control method for process parameters in a supercritical drying production line. This method acquires information on the distribution of solvent within the gel inside the reactor, the purity of the circulating carbon dioxide fluid at the reactor inlet, and the concentration of solvent in the fluid at the reactor outlet. By combining this information, it determines whether solvent replacement is complete. This method effectively solves the "double blind spot" problem in existing technologies regarding the actual solvent distribution within the gel and the changes in the state of the circulating fluid. Specifically, by real-time monitoring of the microscopic distribution of solvent within the gel, it overcomes the shortcomings of traditional methods that rely solely on macroscopic temperature and pressure data and cannot detect solvent retention deep within the gel. Simultaneously, by monitoring the purity of the circulating carbon dioxide fluid, it solves the problem of decreased extraction efficiency and deteriorated product performance caused by circulating fluid contamination. Therefore, this application can avoid gel structure collapse caused by premature entry into the depressurization stage due to misjudgment and effectively prevent performance degradation in subsequent batches of products due to circulating fluid contamination. This significantly improves product performance consistency, reduces the scrap rate, and achieves precise control of the supercritical drying process and stable improvement in product quality. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a method for intelligent control of process parameters in a supercritical drying production line provided by an embodiment of the present invention; Figure 2 This is a schematic diagram of another intelligent control method for process parameters of a supercritical drying production line provided in this embodiment of the invention; Figure 3This is a schematic diagram of the intelligent control system for process parameters of a supercritical drying production line provided in an embodiment of the present invention. Detailed Implementation

[0016] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0017] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0018] To better understand the technical solution proposed in this application, some key terms involved will be explained first.

[0019] The "supercritical drying production line" mentioned in this application refers to an industrial production line that uses supercritical fluid (usually supercritical carbon dioxide) as an extractant to remove solvent from wet gels, thereby preparing porous materials. This production line typically includes key equipment such as reaction vessels, circulating pumps, heaters, and separators. The "reaction vessel" is the core container for solvent replacement, where the wet gel comes into contact with supercritical carbon dioxide fluid to achieve solvent extraction. The "gel" refers to the wet porous material precursor processed during supercritical drying, which contains the solvent to be removed. "Solvent replacement" refers to the process where supercritical carbon dioxide fluid enters the gel, dissolving and carrying away the solvent from the gel pores.

[0020] The following specific embodiments will provide a detailed introduction and explanation of the intelligent control method for process parameters of a supercritical drying production line provided in this application.

[0021] Reference Figure 1 This invention provides an intelligent control method for process parameters in a supercritical drying production line, comprising the following steps: S1, inside the reactor, obtain information on the distribution of the solvent inside the gel.

[0022] This information can be obtained in several ways. For example, magnetic resonance imaging (MRI) can be used to scan hydrogen nuclei in different regions within the gel and analyze their relaxation time differences, thereby inferring the solvent distribution. Another approach is to use X-ray computed tomography (CT) to analyze the attenuation differences of X-rays after penetrating the gel, constructing a density distribution map within the gel, thus indirectly reflecting the solvent distribution. Alternatively, a micro-sensor array embedded within the gel can be used to monitor the dielectric constant or conductivity at different locations in real time. Changes in these parameters are closely related to the solvent content, thus obtaining information about the solvent distribution.

[0023] S2. Obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the concentration information of the solvent in the fluid at the reactor outlet.

[0024] The purity information of the circulating carbon dioxide fluid at the reactor inlet can be obtained using gas chromatography-mass spectrometry (GC-MS). Specifically, small samples can be periodically extracted from the inlet fluid, and the types and contents of residual solvents can be analyzed by GC-MS to assess the purity of the carbon dioxide fluid. Another method is to use Fourier transform infrared spectroscopy (FTIR) to analyze the absorption of the inlet fluid at specific infrared wavelengths, identify and quantify the solvent components, and thus obtain purity information. For the solvent concentration information in the reactor outlet fluid, an online densitometer or refractometer can be used for real-time monitoring. When the solvent is carried out of the reactor by supercritical carbon dioxide, the density or refractive index of the outlet fluid will change, and the solvent concentration can be calculated using a calibration curve. Alternatively, a UV-Vis spectrophotometer can be used to analyze the outlet fluid. If the solvent has characteristic absorption peaks in the UV or visible light region, the solvent concentration can be quantified by the absorption intensity.

[0025] S3. Based on the comprehensive distribution status information, purity information, and solvent concentration information in the fluid at the reactor outlet, determine whether solvent replacement is complete.

[0026] This discrimination process can be based on preset thresholds. For example, when the solvent content in all regions inside the gel is lower than a preset solvent content threshold, it can be preliminarily considered that the solvent inside the gel has been largely removed. Simultaneously, when the purity of the circulating carbon dioxide fluid is greater than a preset purity threshold, it indicates that the carbon dioxide fluid used for extraction has sufficient extraction capacity. Furthermore, when the solvent concentration in the fluid at the reactor outlet is less than a preset concentration threshold, the solvent removal efficiency is further confirmed. Only when all three conditions are met simultaneously can the completion of solvent replacement be definitively determined. This comprehensive discrimination method avoids misjudgments that may arise from a single indicator, improving the accuracy and reliability of the discrimination.

[0027] This application presents an intelligent control method for process parameters in a supercritical drying line. By acquiring information on the distribution of solvents within the gel inside the reactor, it solves the problem of traditional methods being unable to detect microscopic solvent residues within the gel. For example, when different types of solvents are present inside the gel or when the solvent distribution is uneven, traditional methods rely solely on macroscopic temperature and pressure data, making it difficult to determine whether deep-seated solvents have been sufficiently removed. This application, by directly acquiring the distribution of solvents within the gel, can accurately identify solvent retention areas, providing a basis for subsequent process adjustments.

[0028] Meanwhile, this application obtains purity information of the circulating carbon dioxide fluid at the reactor inlet and solvent concentration information of the fluid at the reactor outlet, effectively solving the problem of the impact of circulating carbon dioxide fluid purity changes on drying efficiency. During carbon dioxide recycling, the purification device may not completely remove all residual solvent, leading to a decrease in circulating fluid purity. Traditional methods lack effective monitoring of this, which may result in reduced extraction efficiency. This application, by real-time monitoring of inlet fluid purity and outlet fluid solvent concentration, can dynamically assess the effectiveness of the extractant and adjust process parameters in a timely manner, ensuring the efficiency and thoroughness of solvent replacement.

[0029] Ultimately, this application comprehensively utilizes the above three types of information to determine whether solvent replacement is complete. This multi-dimensional, real-time data fusion and discrimination mechanism overcomes the "double blind spot" of traditional methods regarding the internal state of the gel and the state of the circulating fluid. By accurately determining the timing of solvent replacement completion, it can avoid gel structure collapse caused by premature pressure reduction and product performance defects caused by incomplete solvent removal. Therefore, this application can significantly improve the control precision of the supercritical drying process and the consistency of product quality.

[0030] Compared to existing technologies, the core innovation of this application lies in the introduction of direct perception of the solvent distribution within the gel and real-time monitoring of the purity of the circulating carbon dioxide fluid. Based on this, a multi-dimensional mechanism for comprehensively determining the completion of solvent replacement is constructed. Traditional methods mainly rely on macroscopic parameters such as temperature and pressure of the reactor, which cannot provide in-depth understanding of the microscopic solvent distribution within the gel, nor can they assess changes in the purity of the circulating carbon dioxide fluid in real time. For example, when processing gels containing mixed solvents, traditional methods may prematurely terminate solvent replacement because they cannot detect the retention of a second, difficult-to-remove solvent deep within the gel, leading to internal structural defects in the product. This application, by obtaining information on the distribution of solvents within the gel, can accurately identify areas of solvent retention, thus avoiding such misjudgments. Furthermore, during carbon dioxide recycling, traditional methods lack effective monitoring of the accumulation of residual solvent in the circulating fluid, which may lead to a decrease in extraction efficiency. This application, by obtaining purity information of the circulating carbon dioxide fluid at the reactor inlet, can assess the effectiveness of the extractant in real time and adjust process parameters accordingly. This comprehensive control method makes the control of the supercritical drying process more precise and intelligent, significantly improving the stability and consistency of product quality, and effectively solving the problems of poor product performance consistency and high scrap rate in existing technologies.

[0031] like Figure 2 As shown, specifically, obtaining information on the distribution of the solvent within the gel includes: S101. Apply a microwave signal to the gel and receive the dielectric response characteristics after the microwave signal interacts with the gel.

[0032] Specifically, applying a microwave signal to a gel refers to the directional transmission of microwave energy of a specific frequency and power to the gel sample inside the reaction vessel using a microwave transmitting device. When this microwave signal penetrates the gel, it interacts with the substances inside, especially the solvent molecules. The dielectric response characteristics after the interaction between the microwave signal and the gel can be understood as capturing the microwave signal after it has been attenuated, reflected, or transmitted through the gel using a microwave receiving device, and analyzing the changes in its amplitude, phase, frequency, and other parameters. These changes constitute the dielectric response characteristics of the gel. Dielectric response characteristics are the electrical properties exhibited by a material under the influence of an electromagnetic field; they are closely related to the composition, structure, density of the material, and the type and content of the solvent it contains.

[0033] S102. Based on dielectric response characteristics, obtain information on the distribution state of the solvent inside the gel.

[0034] Among these, obtaining information on the distribution of solvents within the gel based on dielectric response characteristics refers to processing and analyzing the received dielectric response characteristic data to establish a mapping relationship between the dielectric response characteristics and the solvent distribution within the gel. For example, a pre-established calibration model or algorithm can be used to convert changes in dielectric response characteristics into solvent content or concentration information in different regions within the gel, thereby obtaining the spatial distribution of the solvent within the gel.

[0035] This application's method utilizes the sensitivity of microwaves to polar molecules (such as solvents) by applying microwave signals to a gel and analyzing its dielectric response characteristics. When microwaves penetrate the gel, solvent molecules inside the gel absorb and scatter microwave energy, causing changes in the dielectric response characteristics of the microwave signal. The higher the solvent content or the more uneven the distribution, the more significant the change in dielectric response characteristics. By accurately measuring these dielectric response characteristics and combining them with corresponding physical or empirical models, the solvent content and spatial distribution inside the gel can be deduced. This method avoids the destructive nature of traditional sampling analysis, achieving non-destructive, real-time monitoring of the solvent distribution inside the gel.

[0036] In some embodiments described above, the distribution state information of the solvent inside the gel is obtained based on the dielectric response characteristics after the interaction between the microwave signal and the gel. However, in practical applications, the gel skeleton itself also generates a dielectric response to the microwave signal, which may cause the obtained dielectric response characteristics to include background responses caused by the gel skeleton, thereby affecting the accuracy of obtaining the solvent distribution state information inside the gel. Therefore, this application further proposes a method for obtaining the solvent distribution state information inside the gel based on dielectric response characteristics, which includes the following steps: S201. Estimate the effective dielectric constant of the gel skeleton based on the dielectric response characteristics of the microwave signal.

[0037] Specifically, estimating the effective dielectric constant of a gel skeleton refers to determining the dielectric properties of the gel solid skeleton at microwave frequencies through experimental measurements, theoretical calculations, or model fitting. This effective dielectric constant characterizes the gel skeleton's response to microwave signals.

[0038] S202. Based on the effective dielectric constant, subtract the background response caused by the gel skeleton in the dielectric response characteristics.

[0039] Subtracting the background response caused by the gel skeleton in the dielectric response characteristics can be understood as subtracting or separating the dielectric contribution generated by the structure and composition of the gel skeleton itself from the overall dielectric response signal, so as to obtain the dielectric response caused only by the solvent inside the gel.

[0040] S203. Based on the dielectric response characteristics after subtracting the background response, obtain the distribution state information of the solvent inside the gel.

[0041] In practical applications, obtaining information on the distribution of solvents inside a gel based on the dielectric response characteristics after subtracting the background response refers to using processed dielectric response data that mainly reflects the characteristics of the solvent, and then using a pre-established physical model or calibration curve to invert and calculate the solvent content and its spatial distribution in different regions inside the gel.

[0042] The proposed method first estimates the effective dielectric constant of the gel skeleton and then uses this constant to subtract the background response caused by the gel skeleton from the original dielectric response characteristics, thereby effectively separating the dielectric response of the solvent from that of the gel skeleton. This separation allows for a more accurate reflection of the solvent's distribution within the gel when subsequent information on the solvent distribution based on the dielectric response characteristics is obtained, avoiding interference from the gel skeleton in the measurement results.

[0043] In some preferred embodiments, the effective dielectric constant of the gel skeleton can be obtained by performing microwave dielectric measurements on the dried gel (i.e., a solvent-free gel skeleton) beforehand, or by theoretically estimating it using a physical model of the gel material. For example, a mixed dielectric theory model can be used, combining parameters such as the porosity and density of the gel skeleton to calculate its effective dielectric constant. During actual measurement, after receiving the original dielectric response characteristics after the interaction of the microwave signal with the solvent-containing gel, the pre-obtained or estimated effective dielectric constant of the gel skeleton is substituted into the corresponding calculation model to accurately subtract the background response caused by the gel skeleton. Thus, the dielectric response characteristics purely contributed by the solvent can be used more accurately to invert the content and spatial distribution of the solvent inside the gel, for example, by converting it using a calibration curve of dielectric constant versus solvent content.

[0044] In some embodiments described above, this application proposes obtaining information about the distribution of solvent within a gel by applying a microwave signal to the gel and receiving its dielectric response characteristics. However, in practical applications, the morphology of the gel (e.g., size, shape, density, or porosity) can significantly affect the interaction between the microwave signal and the gel, causing the directly obtained raw dielectric response characteristics to fail to accurately reflect the true distribution of solvent within the gel, thus affecting the accuracy of solvent displacement determination. Failure to address this issue may lead to misjudgments of the degree of solvent displacement within the gel, thereby impacting the quality and production efficiency of supercritical drying products.

[0045] In this regard, this application further proposes to apply a microwave signal to the gel and receive the dielectric response characteristics after the interaction between the microwave signal and the gel, including: S301. Apply a microwave signal to the gel and receive the original dielectric response characteristics after the microwave signal interacts with the gel.

[0046] Specifically, the original dielectric response characteristics refer to the dielectric response data directly measured after a microwave signal passes through or reflects through the gel without any correction. This data may include interference from the gel skeleton structure and morphology on the signal.

[0047] S302. Obtain the morphological parameters of the gel.

[0048] In this context, the morphological parameters of a gel can be understood as quantitative data describing its structural characteristics, such as physical shape, size, density, and porosity. For example, these parameters may include the gel's thickness, cross-sectional area, surface roughness, and internal pore structure distribution. The purpose of obtaining these morphological parameters is to quantify the influence of the gel's own physical properties on microwave signal propagation and interaction.

[0049] S303. Based on the morphological parameters, correct the original dielectric response characteristics to obtain the dielectric response characteristics.

[0050] In practical applications, correcting the original dielectric response characteristics based on morphological parameters refers to using known gel morphology information and specific algorithms or models to eliminate or reduce the background response or interference caused by the gel morphology in the original dielectric response characteristics, thereby obtaining a more accurate and pure dielectric response characteristic that reflects the solvent distribution inside the gel.

[0051] This application addresses the interference of gel morphology on microwave signal measurement results by introducing gel morphology parameters and correcting the original dielectric response characteristics. Specifically, when a microwave signal is applied to a gel, its dielectric response is affected not only by the solvent content within the gel but also by morphology parameters such as the physical structure, size, and shape of the gel skeleton. Without correction, the responses caused by these morphology parameters overlap with the solvent response, leading to inaccurate judgments of solvent distribution. By acquiring the gel's morphology parameters and correcting the original dielectric response characteristics based on these parameters, the background signal caused by gel morphology can be effectively removed, allowing the final dielectric response characteristics to more accurately reflect the true distribution of solvent within the gel.

[0052] In some preferred embodiments, a specific example is illustrated below. Suppose that in a supercritical drying line, the gel within the reactor may exhibit irregular shapes or uneven thicknesses due to the preparation process or its own shrinkage. When a microwave signal is applied to this gel, if only the original dielectric response characteristics are received, the signal attenuation or phase change may partly originate from the thickness differences or shape irregularities of the gel, rather than being entirely determined by the internal solvent content. To address this issue, firstly, the morphological parameters of the gel, such as its precise three-dimensional geometric model and local thickness distribution, can be acquired using a laser scanner or a 3D imaging system. Subsequently, a microwave signal is applied to the gel, and its original dielectric response characteristics are received. Next, based on a pre-established physical model or empirical calibration curve, which describes the background response of the gel skeleton to the microwave signal under different morphological parameters, the influence of morphology on the dielectric response can be determined from a first mapping relationship, which includes different morphological parameters and their influence on the dielectric response. Then, using the acquired gel morphological parameters, the corresponding background response is calculated, and this background response is subtracted from the original dielectric response characteristics. This yields a corrected and more accurate dielectric response characteristic, which more accurately reflects the distribution of solvent within the gel, thus providing a reliable data basis for subsequent solvent displacement discrimination.

[0053] Specifically, in the above-mentioned intelligent control method for process parameters of the supercritical drying production line, the purity information of the circulating carbon dioxide fluid at the reactor inlet can be obtained in the following way.

[0054] S401. An infrared beam is emitted through the circulating carbon dioxide fluid at the inlet of the reactor and the transmitted spectral signal is received.

[0055] Specifically, this step involves detecting the circulating carbon dioxide fluid using infrared spectroscopy. In particular, an infrared light source is configured to emit an infrared beam within a specific wavelength range, which passes through the circulating carbon dioxide fluid at the reactor inlet. As the infrared beam passes through the fluid, different components in the fluid (such as carbon dioxide, residual solvents, etc.) selectively absorb the infrared light of specific wavelengths, causing changes in the intensity and spectral characteristics of the transmitted light. These changes are then received by one or more detectors, forming a transmission spectral signal.

[0056] S402. Based on the spectral signal, obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet.

[0057] The process of obtaining purity information of the circulating carbon dioxide fluid at the reactor inlet based on spectral signals can be understood as analyzing and processing the received transmission spectral signals. Since different substances have unique infrared absorption spectral characteristics, by comparing the transmission spectral signals with standard spectra of known substances, the various components present in the fluid and their relative contents can be identified. For example, by analyzing the intensity of the characteristic absorption peaks of a specific solvent, the concentration of residual solvent in the fluid can be quantified, thereby indirectly or directly obtaining purity information of the circulating carbon dioxide fluid. The aim is to monitor the quality of the carbon dioxide fluid entering the reactor in real time and accurately, ensuring the efficiency of the solvent replacement process and product quality.

[0058] This application utilizes infrared spectroscopy to achieve non-contact, online monitoring of the purity of circulating carbon dioxide fluid at the reactor inlet. Its working principle lies in the unique absorption characteristics of different molecules in the fluid, such as carbon dioxide and any residual solvents present, for specific wavelengths of infrared light. When an infrared beam passes through the fluid, these molecules absorb infrared photons that match their vibrational or rotational energy levels, causing a decrease in transmitted light intensity at specific wavelengths. By analyzing the position and intensity of these characteristic absorption peaks in the transmission spectrum signal, the types of substances present in the fluid can be identified, and their concentrations quantified. For example, if a certain solvent is present in the fluid, it will exhibit a specific absorption peak in the infrared spectrum; the intensity of this absorption peak is positively correlated with the solvent concentration. Therefore, by monitoring these characteristic absorption peaks, the content of residual solvent in the circulating carbon dioxide fluid can be accurately assessed, thereby determining its purity. This method provides rapid and accurate purity data, offering reliable input for subsequent solvent replacement determination.

[0059] In one specific implementation, the aforementioned spectral signal can be set as a Raman scattering signal, and the purity information of the circulating carbon dioxide fluid at the reactor inlet can be obtained based on this signal.

[0060] The spectral signal is a Raman scattering signal. Based on the spectral signal, the purity information of the circulating carbon dioxide fluid at the reactor inlet is obtained, including: S501. Deconvolve the Raman scattering signal.

[0061] Specifically, Raman scattering refers to the inelastic scattering of a portion of light when it strikes a substance, causing a change in the frequency of the scattered light. This change in frequency is related to the vibrational and rotational energy levels of the molecules in the substance. By analyzing Raman scattering spectra, information about the molecular structure of a substance can be obtained. In practical applications, Raman spectroscopy is widely used in fluid composition analysis due to its specific ability to identify molecular fingerprints.

[0062] Deconvolution processing of Raman scattering signals involves using mathematical algorithms to separate multiple overlapping characteristic peaks in the spectrum, thereby obtaining the true spectral information of each independent component. This processing aims to improve spectral resolution and accuracy, particularly in mixture analysis, enabling more precise identification and quantification of different components.

[0063] S502. Based on the characteristic peak positions and intensities of the Raman scattering signal after deconvolution processing, obtain the type and concentration of residual solvent in the circulating carbon dioxide fluid at the reactor inlet to obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet.

[0064] Specifically, each solvent molecule has its unique Raman characteristic peak position. By identifying the position of these characteristic peaks, the type of residual solvent can be determined. Furthermore, the intensity of the characteristic peak is usually proportional to the concentration of the corresponding substance; therefore, by measuring the intensity of the characteristic peak, the concentration of residual solvent can be quantified. This allows for the precise acquisition of purity information for the circulating carbon dioxide fluid at the reactor inlet.

[0065] This application employs Raman scattering signals as a spectroscopic analysis method, leveraging its high specificity for molecular structures to accurately identify various residual solvents that may be present in circulating carbon dioxide fluid. Given that industrial fluids may contain multiple solvents or impurities, their spectral signals may overlap. Therefore, deconvolution processing of the Raman scattering signals can effectively separate overlapping characteristic peaks, thereby improving the accuracy of identifying different components. It is precisely because of this high resolution and specificity that, by analyzing the position and intensity of the characteristic peaks in the deconvolutioned Raman scattering signal, the type and concentration of residual solvents can be accurately obtained, thus enabling precise assessment of the purity of the circulating carbon dioxide fluid at the reactor inlet.

[0066] Specifically, the steps for determining whether solvent replacement is complete can be further refined into the following specific operations.

[0067] Based on the above comprehensive distribution status information, purity information, and solvent concentration information in the fluid at the reactor outlet, the determination of whether solvent replacement is complete includes: S601. Based on the distribution status information, determine whether the solvent content in all regions inside the gel is lower than the preset solvent content threshold.

[0068] The "preset solvent content threshold" refers to the critical value at which the solvent content inside the gel is considered to have reached a state of sufficient replacement during the solvent replacement process. This threshold is typically set based on the performance requirements of the target product, the initial solvent content of the gel, and process experience. Its purpose is to ensure that the solvent inside the gel is sufficiently removed to avoid structural collapse or performance defects during subsequent drying. In practical applications, this threshold can be a percentage value; for example, the condition is considered met when the solvent content in all areas inside the gel is below 5%.

[0069] S602. Based on the purity information, determine whether the purity of the circulating carbon dioxide fluid is greater than the preset purity threshold.

[0070] The "preset purity threshold" refers to the minimum purity standard that the circulating carbon dioxide fluid should meet when entering the reactor. This threshold aims to ensure that the carbon dioxide fluid used for displacement does not contain excessive impurities or residual solvents, thereby ensuring its efficient extraction of solvent from the gel. For example, this condition is considered met when the purity of the circulating carbon dioxide fluid is greater than 99.5%.

[0071] S603. Based on the concentration information of the solvent in the fluid at the outlet of the reactor, determine whether the concentration of the solvent in the fluid at the outlet of the reactor is greater than the preset concentration threshold.

[0072] The "preset concentration threshold" refers to the upper limit of the solvent concentration in the fluid exiting the reactor. When the solvent concentration in the outlet fluid is below this threshold, it indicates that very little solvent has been removed from the gel, and the solvent replacement process is nearing completion. This threshold is used to determine the dynamic equilibrium state of solvent replacement, with the aim of avoiding unnecessary process time extension. For example, when the solvent concentration in the outlet fluid is less than 0.1%, this condition is considered met.

[0073] S604. Solvent replacement is determined to be complete when the solvent content in all regions inside the gel is lower than the preset solvent content threshold, the purity of the circulating carbon dioxide fluid is greater than the preset purity threshold, and the concentration of solvent in the fluid at the reactor outlet is less than the preset concentration threshold.

[0074] This application's solution establishes a multi-dimensional, mutually verifying discrimination mechanism by comprehensively considering the actual distribution of solvent within the gel, the purity of the replacement medium (circulating carbon dioxide fluid), and the dynamic efficiency of solvent removal (solvent concentration in the reactor outlet fluid). Specifically, when the solvent content in all regions within the gel is below a preset solvent content threshold, it indicates that the gel matrix has completed solvent removal. Simultaneously, when the purity of the circulating carbon dioxide fluid is greater than a preset purity threshold, the effectiveness of the replacement medium is ensured. Furthermore, when the solvent concentration in the reactor outlet fluid is less than a preset concentration threshold, it further confirms that the solvent removal rate has significantly decreased, indicating that the solvent replacement process has stabilized and been completed. This comprehensive discrimination method effectively avoids misjudgments that may arise from a single indicator. For example, a low outlet solvent concentration alone may not reflect the presence of high solvent content in localized areas within the gel.

[0075] In some embodiments described above, this application proposes using information on the distribution of solvent within the gel, the purity of the circulating carbon dioxide fluid at the reactor inlet, and the concentration of solvent in the fluid at the reactor outlet to determine whether solvent replacement is complete. However, in actual supercritical drying processes, solvent replacement within the gel may be uneven or inefficient, especially when the solvent content is high in certain areas and its reduction rate is slow. Relying solely on monitoring and determination may not effectively accelerate the entire replacement process, thus affecting drying efficiency and product quality.

[0076] In this regard, this application further proposes that the above method also includes: S701. When the solvent content in a certain area inside the gel is higher than the preset solvent content threshold, and the rate of decrease of the solvent content is less than the rate threshold, an auxiliary co-solvent is injected into the circulating carbon dioxide fluid, and microwave energy in the form of pulses is emitted to the gel to promote solvent replacement.

[0077] Specifically, when monitoring the solvent distribution within the gel reveals that certain regions still have high solvent content, and the rate of solvent content reduction in these regions is significantly lower than a preset threshold, it indicates that the solvent replacement process is hindered or inefficient in these areas. In such cases, two synergistic measures can be taken to accelerate and optimize the solvent replacement process. First, injecting an auxiliary co-solvent into the circulating carbon dioxide fluid involves adding a small amount of a substance that is well miscible with both the target solvent and carbon dioxide to the circulating carbon dioxide fluid entering the reactor during supercritical drying. This auxiliary co-solvent can effectively increase the solubility of the target solvent in supercritical carbon dioxide, reducing the mass transfer resistance of solvent diffusion from the gel interior to the fluid, thereby accelerating solvent extraction and replacement. Common auxiliary co-solvents include ethanol, acetone, or methanol, the choice of which usually depends on the properties of the solvent to be replaced in the gel. Second, emitting pulsed microwave energy into the gel involves using microwave radiation to locally or globally heat the gel interior. Microwave energy can selectively heat solvent molecules within the gel, giving them higher kinetic energy and thus accelerating the diffusion rate of solvent molecules. Using pulsed microwave energy can avoid overall gel overheating that could lead to structural damage. It also allows for more precise control of energy input, enabling fine-tuning of the solvent displacement rate. In particular, for regions within the gel with high solvent content and slow displacement, microwave heating can significantly enhance solvent migration.

[0078] This application's solution effectively addresses the problem of uneven or inefficient solvent replacement within gels by synergistically injecting an auxiliary co-solvent and emitting pulsed microwave energy. Specifically, when regions with slow solvent replacement are detected within the gel, the injection of the auxiliary co-solvent significantly enhances the solubility of residual solvent within the gel by supercritical carbon dioxide, reducing the mass transfer resistance of solvent diffusion from the gel pores to the external fluid, thereby accelerating solvent extraction. Simultaneously, pulsed microwave energy selectively heats solvent molecules within the gel, increasing their kinetic energy and diffusion rate. Microwave heating effectively promotes desorption and migration, especially for solvents bound by the gel framework or located in deeper regions. The combination of these two mechanisms, acting on both solubility and diffusion kinetics, overcomes the bottleneck in the solvent replacement process, ensuring complete solvent replacement within the gel.

[0079] In some preferred embodiments, it is assumed that during the supercritical drying process, monitoring of microwave dielectric response characteristics reveals that in a certain batch of silica aerogel, the solvent (e.g., ethanol) content in the central region inside the reactor remains above 5% (a preset solvent content threshold) after a certain stage of replacement, and the rate of decrease in content is below 0.1% / hour (a rate threshold). At this point, the control system will automatically trigger optimization measures. Specifically, acetone can be injected into the circulating carbon dioxide fluid entering the reactor at a ratio of 0.5% (mass concentration) as an auxiliary co-solvent. Simultaneously, a microwave transmitter emits microwave energy at a frequency of 2.45 GHz, a power of 500 W, a pulse width of 100 ms, and a period of 1 s onto the gel, continuously for 10 minutes. Through this synergistic effect, acetone increases the solubility of ethanol in supercritical carbon dioxide, while the pulsed microwaves promote the diffusion and desorption of ethanol molecules within the gel, thereby effectively accelerating solvent replacement in the central region, rapidly reducing the solvent content below the threshold, and ensuring uniform drying of the entire gel.

[0080] The injection rate of the auxiliary co-solvent satisfies the following relationship: V =(C_target F) / (rho_cosolvent); Where V is the injection rate of the auxiliary cosolvent, C_target is the mass concentration of the auxiliary cosolvent in the circulating carbon dioxide fluid, F is the flow rate of the circulating carbon dioxide fluid, and rho_cosolvent is the density of the auxiliary cosolvent.

[0081] Specifically, V refers to the volumetric flow rate of the auxiliary cosolvent injected into the reactor per unit time, typically measured in volumes per second (e.g., liters per minute or cubic meters per hour). C_target can be understood as the desired target mass concentration of the auxiliary cosolvent in the circulating carbon dioxide fluid. Its set value is usually based on experimental data, simulation results, or process experience to ensure that solvent replacement efficiency is maximized without affecting the properties of supercritical carbon dioxide. F refers to the volumetric flow rate of the circulating carbon dioxide fluid through the reactor, which can be obtained in real time through a flow meter. rho_cosolvent refers to the density of the auxiliary cosolvent at the operating temperature and pressure; this parameter can be obtained by consulting physical property data or actual measurement. Using the above formula, the required auxiliary cosolvent injection rate can be accurately calculated based on the preset target concentration and actual process parameters.

[0082] This application solves the problem of precisely controlling the amount of auxiliary co-solvent injected in the aforementioned technical solutions by providing a clear mathematical relationship to calculate the injection rate. Because this formula dynamically determines the required injection rate based on the real-time flow rate of the circulating carbon dioxide fluid and the desired target concentration of the co-solvent, the auxiliary co-solvent can be introduced into the supercritical drying line in the optimal ratio. This precise control ensures that the auxiliary co-solvent is maintained at a constant and effective concentration level in the circulating carbon dioxide fluid, thereby optimizing the interaction between the solvent and the solvent inside the gel, accelerating the diffusion and replacement process of the solvent inside the gel, and avoiding excessive or insufficient use of the co-solvent, thus improving the efficiency and stability of the entire solvent replacement process.

[0083] like Figure 3 As shown in the figure, this embodiment of the invention also provides an intelligent control system for process parameters of a supercritical drying production line, used in a supercritical drying production line, which includes a reaction vessel. The system includes: The acquisition module is used to acquire information about the distribution of solvent inside the gel within the reactor. The spectral analysis module is used to obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the solvent concentration information in the fluid at the reactor outlet. The solvent replacement discrimination module is used to determine whether solvent replacement has been completed by comprehensively considering the distribution status information, purity information, and solvent concentration information in the fluid at the reactor outlet.

[0084] This application also provides a computer-readable storage medium. All or part of the processes in the above method embodiments can be executed by a computer program instructing related hardware. This program can be stored in the computer-readable storage medium, and when executed, it can include the processes of the above method embodiments. The computer-readable storage medium can be an internal storage unit of the task execution device (including a data sending end and / or a data receiving end) of any of the foregoing embodiments, such as the hard disk or memory of the task execution device. The computer-readable storage medium can also be an external storage device of the terminal device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal device. Further, the computer-readable storage medium can include both the internal storage unit of the task execution device and an external storage device. The computer-readable storage medium is used to store the computer program and other programs and data required by the task execution device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0085] 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.

[0086] 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, essentially, 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, ROM, RAM, magnetic disks, or optical disks.

[0087] The above are merely specific embodiments 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 covered within the scope of protection of this application.

Claims

1. A method for intelligent control of process parameters in a supercritical drying production line, characterized in that, For use in a supercritical drying production line, the supercritical drying production line includes a reaction vessel, comprising: Inside the reaction vessel, information on the distribution of the solvent within the gel is obtained; Obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the solvent concentration information of the fluid at the reactor outlet; By combining the distribution status information, the purity information, and the solvent concentration information in the fluid at the reactor outlet, it is determined whether solvent replacement has been completed.

2. The intelligent control method for process parameters of a supercritical drying production line according to claim 1, characterized in that, The process of obtaining information on the distribution of solvent within the gel includes: A microwave signal is applied to the gel, and the dielectric response characteristics after the interaction between the microwave signal and the gel are received; Based on the dielectric response characteristics, the distribution state information of the solvent inside the gel is obtained.

3. The intelligent control method for process parameters of a supercritical drying production line according to claim 2, characterized in that, The step of obtaining the distribution state information of the solvent inside the gel based on the dielectric response characteristics includes: The effective dielectric constant of the gel skeleton is estimated based on the dielectric response characteristics of the microwave signal. Based on the effective dielectric constant, the background response caused by the gel skeleton in the dielectric response characteristics is subtracted; Based on the dielectric response characteristics after subtracting the background response, the distribution state information of the solvent inside the gel is obtained.

4. The intelligent control method for process parameters of a supercritical drying production line according to claim 2, characterized in that, Applying a microwave signal to a gel and receiving the dielectric response characteristics after the interaction of the microwave signal with the gel, including: A microwave signal is applied to the gel, and the original dielectric response characteristics after the microwave signal interacts with the gel are received; Obtain the morphological parameters of the gel; The original dielectric response characteristics are corrected based on the morphological parameters to obtain the dielectric response characteristics.

5. The intelligent control method for process parameters of a supercritical drying production line according to claim 1, characterized in that, The process of obtaining the purity information of the circulating carbon dioxide fluid at the reactor inlet includes: An infrared beam is emitted through the circulating carbon dioxide fluid at the inlet of the reactor, and the transmitted spectral signal is received; Based on the spectral signal, the purity information of the circulating carbon dioxide fluid at the reactor inlet is obtained.

6. The intelligent control method for process parameters of a supercritical drying production line according to claim 5, characterized in that, The spectral signal is a Raman scattering signal. The process of obtaining purity information of the circulating carbon dioxide fluid at the reactor inlet based on the spectral signal includes: The Raman scattering signal is deconvolved. Based on the characteristic peak positions and intensities of the Raman scattering signal after deconvolution processing, the type and concentration of residual solvent in the circulating carbon dioxide fluid at the reactor inlet are obtained to acquire purity information of the circulating carbon dioxide fluid at the reactor inlet.

7. The intelligent control method for process parameters of a supercritical drying production line according to claim 1, characterized in that, Based on the distribution status information, purity information, and solvent concentration information in the fluid at the reactor outlet, the determination of whether solvent replacement is complete includes: Based on the distribution status information, determine whether the solvent content in all regions inside the gel is lower than a preset solvent content threshold. Based on the purity information, determine whether the purity of the circulating carbon dioxide fluid is greater than a preset purity threshold; Based on the concentration information of the solvent in the fluid at the outlet of the reactor, determine whether the concentration of the solvent in the fluid at the outlet of the reactor is greater than a preset concentration threshold; Solvent replacement is determined to be complete when the solvent content in all regions inside the gel is lower than a preset solvent content threshold, the purity of the circulating carbon dioxide fluid is greater than a preset purity threshold, and the concentration of solvent in the fluid at the reactor outlet is less than a preset concentration threshold.

8. The intelligent control method for process parameters of a supercritical drying production line according to claim 1, characterized in that, The method further includes: When the solvent content in a certain area inside the gel is higher than a preset solvent content threshold, and the rate of decrease in solvent content is less than a rate threshold, an auxiliary co-solvent is injected into the circulating carbon dioxide fluid, and microwave energy in the form of pulses is emitted into the gel to promote the replacement of the solvent.

9. The intelligent control method for process parameters of a supercritical drying production line according to claim 8, characterized in that, The injection rate of the auxiliary co-solvent satisfies the following relationship: V = (C_target F) / (rho_cosolvent); Where V is the injection rate of the auxiliary cosolvent, C_target is the mass concentration of the auxiliary cosolvent in the circulating carbon dioxide fluid, F is the flow rate of the circulating carbon dioxide fluid, and rho_cosolvent is the density of the auxiliary cosolvent.

10. An intelligent control system for process parameters of a supercritical drying production line, used in a supercritical drying production line, the supercritical drying production line including a reaction vessel, characterized in that, The system includes: The acquisition module is used to acquire information about the distribution of solvent inside the gel within the reactor. The spectral analysis module is used to obtain the purity information of the circulating carbon dioxide fluid at the reactor inlet and the solvent concentration information in the fluid at the reactor outlet. The solvent replacement discrimination module is used to determine whether solvent replacement is complete by comprehensively considering the distribution state information, the purity information, and the solvent concentration information in the fluid at the reactor outlet.

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