Method for controlling the generation of active radicals in a microwave plasma desmearing process

Abstract

The application provides a method for controlling active free radical generation in a microwave plasma desmear process, comprising: obtaining the concentration of soluble decomposed substances of recycled water, identifying the dielectric properties of a premix solution under a microwave frequency band, and performing adaptive evaluation on the dielectric properties and a preset dielectric threshold; igniting the premix solution entering a main reaction cavity by adapting the excitation intensity of the dielectric load of the premix solution, and obtaining the glow start delay time length in the ignition process; adjusting the discharge channel cross section geometry inside the microwave excitation zone according to the reconstruction mode of the discharge channel of the microwave excitation zone, and forming a discharge excitation pattern adapting to the dielectric properties of the premix solution; controlling the generation process of active free radicals through the discharge excitation pattern, obtaining the expected active free radical generation level, and inhibiting the generation jump of active free radicals.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for regulating the generation of active free radicals during microwave plasma resin removal. Background Technology

[0002] Microwave plasma resin removal technology plays a crucial role in the surface treatment of high-end materials. The stable generation of active free radicals is a core factor determining the quality of resin removal and the reliability of the process. Current conventional control methods often focus on mechanical compensation of external microwave power, neglecting the direct interference of transient changes in the physicochemical properties of the reaction medium on microwave energy absorption efficiency. This results in a lack of timely detection and correction of imbalances in the internal energy coupling state when facing complex operating conditions. In the prior art, a microwave plasma resin removal device, publication number CN113070288A, discloses a technique for microwave plasma resin removal using a microwave device, a quartz cavity, a main cavity, a transfer device, a high-density metal mesh assembly, and a heating plate. The plasma intensity reaching the sample surface can be adjusted according to the amount of resin in the sample. However, this disclosed technique mainly relies on structural components to adjust the plasma intensity, still facing the problem of difficulty in timely detection of microwave energy coupling imbalances caused by fluctuations in the composition of the reaction medium. This leads to glow discharge start-up drift, unstable generation of active free radicals, and potential uneven treatment results or localized material damage. In actual closed-loop rinsing processes, recycled water, after atomization or vaporization, directly enters the microwave coupling zone of the main reaction chamber as a reaction medium to participate in discharge ignition. Here, a potentially overlooked but fatal chain reaction exists: when the concentration of residual soluble decomposition products in the recycled water fluctuates drastically, this change in composition immediately triggers a sudden change in the dielectric properties of the premixed liquid in the microwave band. This drastic change in dielectric state directly disrupts the original microwave impedance matching conditions, severely disturbing the stability of glow discharge initiation. For example, in continuous resin removal operations, if a high concentration of residual decomposition products from the previous batch is suddenly mixed into the recycled water, the premixed liquid, which was originally able to uniformly absorb microwave energy, instantly becomes difficult for microwaves to penetrate, leading to an uncontrollable delay in plasma ignition time. This glow discharge initiation drift causes the originally smoothly generated active free radicals to suddenly and violently jump, directly causing uneven resin removal and even localized material damage. Accurately capturing the dielectric state deviation caused by fluctuations in the composition of the recycled water and effectively suppressing the resulting glow discharge initiation drift and free radical generation jumps becomes a key issue in achieving stable control of the microwave plasma resin removal process. Summary of the Invention

[0003] This invention provides a method for regulating the generation of active free radicals during microwave plasma resin removal, the method comprising: The concentration of soluble decomposition products in the recycled water is obtained, the dielectric properties of the premixed liquid in the microwave band are identified, and the dielectric properties are evaluated to ensure their compatibility with a preset dielectric threshold. If the dielectric properties exceed the preset dielectric threshold, the dielectric properties of the premixed liquid are analyzed to obtain the microwave energy of the main reaction cavity. The microwave energy of the main reaction cavity is then adjusted to obtain the excitation intensity that matches the dielectric load of the premixed liquid. The premixed liquid entering the main reaction chamber is ignited by adapting the excitation intensity of the dielectric load of the premixed liquid, and the glow start delay time during the ignition process is obtained. The glow start delay time is evaluated against a preset time threshold. When the glow start delay time exceeds the preset time threshold, glow start drift is determined to have occurred during the ignition process. When glow discharge drift occurs during ignition, the field strength distribution pattern in the microwave excitation region during the discharge ignition process is extracted, and the field strength distribution pattern is analyzed to determine the reconstruction method of the discharge channel in the microwave excitation region. Adjust the cross-sectional geometry of the discharge channel inside the microwave excitation region according to the reconstruction method of the discharge channel in the microwave excitation region to form a discharge excitation pattern that adapts to the dielectric properties of the premixed liquid. By controlling the generation process of active free radicals through the discharge excitation pattern, the expected level of active free radical generation can be obtained, and abrupt jumps in the generation of active free radicals can be suppressed.

[0004] Furthermore, the acquisition of the concentration of soluble decomposable substances in the recycled water and the identification of the dielectric properties of the premixed liquid in the microwave frequency band include: Continuous sampling and monitoring of the recycled water are conducted to obtain the concentration values ​​of soluble decomposable substances in the recycled water. The concentration values ​​are compared with the baseline reference values ​​of the recycled water to obtain the concentration deviation of soluble decomposable substances and determine the compositional fluctuation characteristics of the premixed liquid input side. Based on the composition fluctuation characteristics, the dielectric constant and loss tangent of the premixed liquid are measured by frequency sweep in the microwave operating frequency band to obtain the dielectric response curves of the premixed liquid at different decomposition product concentrations. The current dielectric property parameters of the premixed liquid are determined based on the dielectric response curves.

[0005] Furthermore, the adaptation evaluation of the dielectric properties with the preset dielectric threshold includes: The current dielectric properties of the premixed liquid are compared with the preset dielectric threshold range to obtain the deviation of the dielectric properties relative to the threshold range. If the deviation exceeds the threshold range, it is determined that the dielectric properties of the premixed liquid in the microwave frequency band have exceeded the limit, and an adaptation evaluation conclusion for the dielectric state of the premixed liquid is obtained.

[0006] Furthermore, if the dielectric properties exceed a preset dielectric threshold, the dielectric properties of the premixed liquid are analyzed to obtain the microwave energy of the main reaction cavity. The microwave energy of the main reaction cavity is then adjusted to obtain an excitation intensity suitable for the dielectric load of the premixed liquid, including: Based on the normalized distance between the real part of the complex permittivity and the loss tangent exceeding the upper and lower limits of the threshold, the polarization loss variation and microwave energy absorption load magnitude of the premixed liquid are obtained. Combining the cumulative distribution of the variation and load magnitude in the coupling region of the main reaction cavity, the microwave energy supply of the main reaction cavity is obtained. The reflection coefficient and transmission coefficient of the microwave feed port of the main reaction cavity are scanned and measured according to the microwave energy supply to determine the microwave excitation operating point of the main reaction cavity. The output power and feed phase of the microwave source, as well as the insertion depth of the tuning screw of the rectangular waveguide section, are adjusted in conjunction with the microwave excitation operating point. The convergence is determined by the power density at the coupling loss point falling back to the preset power threshold range, thus obtaining the excitation intensity of the premixed liquid dielectric load.

[0007] Furthermore, the step of igniting the premixed liquid entering the main reaction chamber by adapting the excitation intensity of the premixed liquid dielectric load to obtain the glow discharge start-up delay time during the ignition process includes: Microwave-feed ignition is performed on the premixed liquid entering the main reaction chamber, and the start time of the excitation intensity at the feed port is recorded to obtain the triggering point of the ignition process. The glow emission signal of the premixed liquid is continuously collected by a photodetector installed in the observation window of the main reaction chamber. The moment when the glow emission signal first exceeds the preset glow intensity threshold is captured. The difference between the moment and the triggering start point of the ignition process is calculated to obtain the glow start delay time.

[0008] Furthermore, the evaluation of the glow start delay duration and a preset time threshold, and the identification of glow start drift in the ignition process when the glow start delay duration exceeds the preset time threshold, includes: The glow discharge start-up delay duration is compared with a preset duration threshold, which is set based on the upper limit of the glow discharge start-up delay duration under stable batch conditions, to obtain an over-limit indicator of the glow discharge start-up delay duration relative to the preset duration threshold; Based on the over-limit indicator, the over-limit amplitude is characterized, and the over-limit amplitude is used as a measure of the drift degree to identify the glow start drift that occurred during this ignition process.

[0009] Furthermore, during the glow discharge drift at the extraction ignition point, the field strength distribution pattern within the microwave excitation region during the discharge ignition process is analyzed to determine the reconstruction method of the discharge channel in the microwave excitation region, including: Based on the pre-calibrated electric field probe grid's location in the microwave excitation region, the amplitude and phase of the electric field vector at each probe node are recorded synchronously to obtain the field strength distribution pattern. The amplitude gradient is extracted node by node along the axial and radial directions of the microwave excitation region to obtain the distribution of high-intensity dense region and weak-field low-lying region in the microwave excitation region. For the transition boundary between the high-intensity dense region and the weak-field low-lying region, the deviation path and deviation direction of the discharge carriers are obtained. Based on the deviation path and the deviation orientation, the expansion direction of the discharge channel cross-section is obtained by considering the aggregation direction of the deviation path in the high-intensity dense region, and the retraction direction of the discharge channel cross-section is obtained by considering the bypass direction of the deviation path in the weak-field low-lying region. Combining the transition contour of the expansion direction and the retraction direction along the axial direction of the microwave excitation region, the cross-sectional geometric reconstruction method of the discharge channel in the microwave excitation region is determined.

[0010] Furthermore, adjusting the cross-sectional geometry of the discharge channel within the microwave excitation region according to the reconstruction method of the discharge channel in the microwave excitation region to form a discharge excitation pattern adapted to the dielectric properties of the premixed liquid includes: The target cross-sectional center offset and the ratio of the major and minor axes of the target cross-section to the inflection point of the target boundary are extracted from each segment along the axial direction of the discharge channel to obtain the target vector for adjusting the geometry of the discharge channel cross-section. Based on the adjustment target vector, the cavity constraint component and magnetic constraint coil in the microwave excitation region are driven in a linkage with the airflow deflector plate to obtain the actual cross-sectional geometry of the discharge channel in the microwave excitation region. Based on the spatial correspondence between the actual cross-sectional geometry and the dielectric properties of the premixed liquid in the reconstructed channel, the uniform distribution of electric field intensity along the cross-section of the discharge channel and the continuous absorption direction of microwave energy along the axial direction are obtained, forming a discharge excitation pattern adapted to the dielectric properties of the premixed liquid.

[0011] Furthermore, controlling the generation process of reactive free radicals through the discharge excitation pattern to obtain the expected level of reactive free radical generation and suppress abrupt changes in the generation of reactive free radicals includes: By applying a uniform field strength and continuous absorption direction to the discharge channel in the microwave excitation region using the discharge excitation pattern adapted to the dielectric properties of the premixed liquid, the dissociation and collision activity of the premixed liquid molecules are obtained, and the generation process of active free radicals, as well as their instantaneous generation rate and cumulative generation level, are determined.

[0012] Furthermore, determining the generation process of active free radicals and their instantaneous generation rate and cumulative generation level includes: The intensity of characteristic emission lines of active free radicals is collected in real time by an emission spectrometer set at the outlet section of the main reaction chamber. The measured sequence of instantaneous generation rate and cumulative generation level of the active free radicals is obtained based on the intensity of the characteristic emission lines. The measured sequence is compared with the expected generation level to obtain the generation level deviation and generation rate fluctuation amplitude. Based on the deviation of the generation level and the fluctuation amplitude of the generation rate, the cross-sectional morphology parameter set and axial power distribution curve in the discharge excitation pattern are finely adjusted in a loop to bring the instantaneous generation rate back to the expected allowable band, suppress the sudden jump in the generation of active free radicals, and obtain the expected level of active free radical generation.

[0013] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a method for regulating the generation of active free radicals during microwave plasma resin removal. Addressing the problem of fluctuations in the dielectric properties of the premixed solution caused by changes in the concentration of soluble decomposable substances in recycled water, leading to glow discharge delay and discharge channel drift in the microwave excitation region, this invention identifies the dielectric properties of the premixed solution in the microwave band in real time and evaluates their compatibility with preset thresholds. When the dielectric properties exceed the threshold, the microwave energy of the main reaction cavity is dynamically adjusted to match the dielectric load of the premixed solution. When the glow discharge delay during the ignition process exceeds the preset threshold, the field strength distribution pattern during the discharge ignition process in the microwave excitation region is extracted and analyzed. Based on this, the reconstruction method of the discharge channel is determined. By adjusting the cross-sectional geometry of the discharge channel within the microwave excitation region, a discharge excitation pattern adapted to the dielectric properties of the premixed solution is formed, thereby precisely controlling the generation process of active free radicals, obtaining the expected level of active free radical generation, effectively suppressing abrupt jumps in active free radical generation caused by dielectric property fluctuations, and improving the stability and controllability of the resin removal process. Attached Figure Description

[0014] Figure 1 This is a flowchart of a method for regulating the generation of active free radicals during microwave plasma resin removal according to the present invention.

[0015] Figure 2 This is a schematic diagram of a method for regulating the generation of active free radicals during microwave plasma resin removal according to the present invention.

[0016] Figure 3 This is another schematic diagram of a method for regulating the generation of active free radicals during microwave plasma resin removal according to the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figures 1 to 3 This embodiment of a method for regulating the generation of active free radicals during microwave plasma resin removal may specifically include: Step S101: Obtain the concentration of soluble decomposition products in the recycled water, identify the dielectric properties of the premixed liquid in the microwave frequency band, and evaluate the compatibility of the dielectric properties with the preset dielectric threshold.

[0019] Continuous sampling and monitoring of recycled water using an online total organic carbon analyzer and conductivity sensor were conducted to obtain the concentration values ​​of soluble decomposable substances in the recycled water. These concentration values ​​were compared with baseline reference values ​​for recycled water to determine the concentration deviation of soluble decomposable substances, thus identifying the compositional fluctuation characteristics of the premixed liquid input. Based on these compositional fluctuation characteristics, a vector network analyzer was used to perform frequency sweep measurements of the dielectric constant and loss tangent of the premixed liquid in the microwave operating frequency band, obtaining dielectric response curves of the premixed liquid at different decomposable substance concentrations. The current dielectric property parameters of the premixed liquid were determined based on these dielectric response curves. These dielectric property parameters were compared with a pre-set dielectric threshold range to obtain the deviation of the dielectric property parameters relative to the threshold range. If the deviation exceeds the threshold range, it is determined that the dielectric properties of the premixed liquid in the microwave frequency band have exceeded the limit, resulting in an adaptation evaluation conclusion for the dielectric state of the premixed liquid.

[0020] In the microwave plasma resin removal process, recycled water, after atomization or vaporization, forms a premixed liquid which serves as the reaction medium and enters the microwave coupling zone of the main reaction chamber for discharge ignition. The soluble decomposable substances within this premixed liquid include both organic carbon components and inorganic ionic residues. Fluctuations in their concentration directly alter the premixed liquid's absorption behavior of microwave energy. Therefore, online sensing of the recycled water composition and the dielectric state of the premixed liquid constitutes the front-end of the entire control chain. In one embodiment, an online total organic carbon analyzer is installed on a branch of the recycled water return pipeline, sampling the recycled water at intervals of 1 to 5 minutes to measure the total organic carbon content. Simultaneously, a conductivity sensor is embedded at the flange interface of the main pipeline to continuously measure the conductivity of the recycled water. The measured conductivity reflects the accumulation level of inorganic ionic residues in the recycled water.

[0021] Specifically, the total organic carbon (TOC) content and conductivity reading together constitute the concentration of soluble decomposables. The baseline reference value for the recycled water is taken from the initial state of the recycled water at the beginning of the process, i.e., the initial recycled water before entering the discharge unit and after only routine filtration and proportioning. The typical range for TOC is 2 to 5 mg / L, and the typical range for conductivity is 50 to 200 μSiemens / cm. The TOC and conductivity collected under this initial state are used as the baseline values. Subtracting the baseline reference value from the concentration value yields the concentration offset, which characterizes the increase in soluble decomposables introduced during the discharge process.

[0022] In one embodiment, concentration shifts are monitored in real time at 10-second sampling intervals during continuous operation, resulting in a concentration shift sequence over time. This sequence exhibits a step-like change on a minute-level timescale, remaining relatively stable between adjacent steps but experiencing a jump at the step transition point. The difference in concentration shifts between adjacent steps is denoted as the jump amplitude A, and the duration of each step is denoted as T. A and T together constitute the component fluctuation characteristics on the premixed liquid input side, typically with A ranging from 0.5 to 2.0 units and T ranging from 1 to 5 minutes. This component fluctuation characteristic is extracted after the concentration shift monitoring is completed and used as the input basis for subsequent frequency sweep measurements.

[0023] It should be noted that the premixed liquid is formed by mixing recycled water, atomized through an atomizing nozzle, with carrier gas in a premixing chamber. The recycled water originates from the purified effluent of a wastewater treatment system and contains soluble decomposable substances of the material to be treated, namely small-molecule water-soluble products generated during the pre-pyrolysis stage of organic matter, with a concentration ranging from 500 to 3000 mg / L. The carrier gas is nitrogen or air, with a flow rate of 10 to 50 standard cubic meters per hour. The premixing chamber is a cylindrical cavity with a diameter of 100 to 300 mm and a height of 150 to 400 mm, and is equipped with internal guide plates to promote uniform gas-liquid mixing. The dielectric response of the formed premixed liquid in the microwave frequency band is directly governed by the concentration of soluble decomposable substances; the higher the concentration, the larger the dielectric constant ε and dielectric loss factor tanδ, and the stronger the microwave absorption capacity.

[0024] Preferably, a vector network analyzer is used to sweep the premixed liquid in two adjacent sub-bands of the microwave operating frequency band. The sweep signal is coupled to the measurement window of the premixed cavity through a coaxial probe. The reflection coefficient and transmission coefficient are converted by the calibration model inside the vector network analyzer and the complex permittivity is output.

[0025] It is understandable that the complex permittivity comprises two terms: a real part and an imaginary part. The real part characterizes the energy storage capacity of the premixed liquid for a microwave electric field, while the imaginary part reflects the degree of microwave energy dissipation within the premixed liquid. The ratio of the two is the loss tangent. ,in Let be the real part of the complex permittivity. The imaginary part of the complex dielectric constant is represented by ε' and ε″. During the frequency sweep, each frequency point corresponds to a set of ε′ and ε″ values, and the values ​​of all frequency points are connected to form a dielectric response curve. Further, the complex dielectric constant value and loss tangent value of the center operating frequency point are extracted from the dielectric response curve, and combined with the slope trend of adjacent frequency points, the microwave absorption intensity and polarization loss degree of the premixed liquid in this operating frequency band are characterized. The resulting numerical combination is used as the current dielectric characteristic parameter of the premixed liquid. The dielectric threshold range is set according to the historical stable discharge data of the main reaction cavity.

[0026] Specifically, several batches of data with stable glow discharge start-up and free radical generation levels within the expected range are selected from historical operation archives. The real part of the complex permittivity and the loss tangent of the corresponding premixed liquids of these batches are extracted, and their lower and upper envelopes are taken as the lower and upper limits of the threshold interval, respectively.

[0027] In one embodiment, the dielectric property parameter is compared with a pre-set dielectric threshold range. The deviation is measured by the normalized distance of the dielectric property parameter exceeding the upper or lower limit of the threshold. The normalized distance is the larger of the real part deviation and the loss tangent deviation. If the deviation exceeds the threshold range, it is determined that the dielectric properties of the premixed liquid have exceeded the limit in the microwave frequency band, and an adaptation evaluation conclusion for the dielectric state of the premixed liquid is obtained.

[0028] For example, when switching batches during continuous resin removal operations, a high concentration of residual decomposition products from the previous batch suddenly mixes into the recycled water, causing a step-like jump in concentration deviation. Consequently, the loss tangent of the premixed liquid increases significantly and exceeds the upper limit of the threshold. The adaptation evaluation conclusion is marked as an over-limit state, which serves as the triggering basis for subsequent microwave excitation intensity adjustment actions.

[0029] Step S102: If the dielectric properties exceed the preset dielectric threshold, the dielectric properties of the premixed liquid are analyzed to obtain the microwave energy of the main reaction cavity, and the microwave energy of the main reaction cavity is adjusted to the excitation intensity that matches the dielectric load of the premixed liquid.

[0030] If the adaptation evaluation conclusion indicates that the dielectric properties of the premixed liquid exceed the limit, then based on the normalized distance between the real part of the complex dielectric constant and the loss tangent exceeding the upper and lower limits of the threshold, the polarization loss variation and microwave energy absorption load magnitude of the premixed liquid are obtained. Combining the cumulative distribution of these variation and load magnitude in the coupling region of the main reaction cavity, the microwave energy supply of the main reaction cavity is obtained. Based on the microwave energy supply, a vector network analyzer is used to scan and measure the reflection coefficient and transmission coefficient of the microwave feed port of the main reaction cavity, obtaining the impedance matching state, power density distribution, and coupling loss sites of the main reaction cavity, thus determining the microwave excitation operating point of the main reaction cavity. Based on the microwave excitation operating point, the output power of the microwave source, the feed phase, and the insertion depth of the tuning screw in the rectangular waveguide section are adjusted in a coordinated manner. The convergence is determined when the power density at the coupling loss sites falls back to the preset power threshold range, thus obtaining the excitation intensity of the microwave energy adaptation premixed liquid dielectric load of the main reaction cavity.

[0031] Following the previous adaptation evaluation stage, when the adaptation evaluation conclusion indicates that the dielectric properties of the premixed liquid exceed the limit in the microwave frequency band, the cause of the exceeding the limit is analyzed, and the microwave energy supply corresponding to the main reaction cavity is deduced from the dielectric load, which constitutes the entry action of this stage.

[0032] Specifically, the complex permittivity of the premixed liquid includes the real part. With the imaginary part Two items, loss tangent The real part reflects the energy storage level, and the loss tangent reflects the dissipation level. The normalized distance Dε between the real part of the complex permittivity and the upper and lower limits of the threshold is denoted as... ,in The median value of the threshold. The median value of the threshold is half the width of the threshold interval; similarly, the normalized distance Dt of the loss tangent is obtained. The median value of the threshold and half the width of the interval are obtained based on the online dielectric test data of qualified batches of premixed liquid under the same temperature and frequency conditions within the past 12 months. After removing abnormal samples that deviate from 3 times the standard deviation, the mean of the remaining samples is taken as the median value. The median value of the threshold corresponding to tanδ is taken as twice the standard deviation. With Δtanδ. Taking a typical water-based premixed solution at 2.45 GHz and 25 degrees Celsius as an example, the statistical sample mean is calculated. The value is approximately 76.5, and the standard deviation is approximately 1.2. The threshold value is set to 2.4; the median value of the tanδ threshold is approximately 0.157, and Δtanδ is set to 0.012. When the production formula, temperature range, or detection frequency changes, at least 30 sets of qualified batch data must be collected again for statistical updates to ensure that the normalized distance reflects the true level of process fluctuation.

[0033] In one embodiment, the normalized distance Dε is converted using a pre-calibrated polarization response mapping table to obtain the polarization loss variation per unit volume of the premixed liquid in the microwave coupling region of the main reaction cavity, i.e., the magnitude of microwave field energy redistribution caused by molecular orientation polarization per unit volume. The mapping table is a two-dimensional data table; the first column records the discrete values ​​of the normalized distance Dε, and the second column records the corresponding polarization loss variation per unit volume ΔP. The sampling interval for Dε is 0.05, covering a range of 0 to 1.5. During the conversion, two adjacent calibration points are found in the mapping table based on the calculated Dε value. Linear interpolation is used to calculate the actual ΔP value. The interpolation formula is: ΔP equals ΔP1 plus the difference between Dε and Dε1 multiplied by the difference between ΔP2 and ΔP1, then divided by the difference between Dε2 and Dε1. Here, Dε1 and Dε2 are two adjacent normalized distance calibration values ​​in the mapping table, and ΔP1 and ΔP2 are the corresponding polarization loss variations. The mapping table is obtained by testing the premixed liquid at 5 to 8 concentration gradients point by point during the initial stage of the process. The test concentration range is 0.1% to 5% mass fraction. Each concentration point is tested 3 times and the average value is taken. The mapping table data is stored in the non-volatile memory of the microwave control system.

[0034] Understandably, after conversion using the loss mapping table, the normalized distance Dt yields the magnitude of the microwave energy absorption load of the premixed liquid. This magnitude of absorption load characterizes the total amount of microwave energy converted into heat and polarization relaxation losses per unit time and unit volume by the premixed liquid. The loss mapping table and the polarization response mapping table are independent of each other. The polarization response mapping table takes the normalized dielectric constant difference Dε as input and outputs a polarization degree parameter, used to evaluate the orientation response intensity of the premixed liquid molecular dipoles in a microwave electric field. The loss mapping table takes the normalized distance Dt as input and outputs the magnitude of the absorption load, used to quantify the rate at which the premixed liquid converts microwave energy into internal energy. These two mapping tables correspond to two independent physical processes: polarization characteristic evaluation and energy loss evaluation, and are used synergistically in predicting microwave heating effects.

[0035] It should be noted that the coupling zone of the main reaction chamber is not a homogeneous medium. The premixed liquid exhibits a bottom-up mist flow distribution and velocity gradient within the coupling zone.

[0036] In one possible implementation, the coupling region is divided into several thin layers along the axial direction. The volume percentage and residence time of each thin layer are determined by the premixed liquid feed flow rate and the atomizing nozzle outlet geometry. The polarization loss variation and absorption load magnitude are weighted layer by layer on each thin layer to obtain the cumulative distribution of the polarization loss variation and load magnitude along the axial direction of the coupling region. This cumulative distribution reflects the overall microwave energy demand and axial distribution bias of the main reaction cavity under this batch of premixed liquid, ultimately summing up to the microwave energy supply of the main reaction cavity. The microwave energy supply includes two core data points: the first is the total power demand value, and the second is the power distribution weight vector along the axial direction of the coupling region. Based on the microwave energy supply, a vector network analyzer is used to perform online measurements at the microwave feed port of the main reaction cavity. The vector network analyzer extracts incident and reflected waves from the feed waveguide through a directional coupler and performs frequency sweep measurements on the reflection coefficient S11 and transmission coefficient S21. S11 reflects the return loss of the feed port under premixed liquid load, and S21 reflects the transmission ratio of microwave energy after entering the coupling region.

[0037] Specifically, the impedance matching state is characterized by the amplitude and phase of S11 at the operating frequency. The closer the amplitude is to 0, the lower the impedance mismatch. The power density distribution P(z) is obtained by multiplying the square of the amplitude of S21 at each sampling position along the axis, |S21(zi)|², by the power allocation weight vector W(zi) point by point, where zi represents the axial coordinate of the i-th thin layer. The calculation result is the actual microwave power density received by each thin layer. The coupling loss point is located as the peak point of the relative deviation Δ(zi) = |P(zi) - W(zi)| / W(zi) between the measured power density P(zi) and the preset weight W(zi) along the axis. The peak point is where the microwave energy does not fall into the corresponding thin layer according to the preset weight. Further, regarding the spatial relationship between the power density distribution and the coupling loss point in the coupling region, |S11| and the root mean square deviation of the power density σ are first normalized to dimensionless quantities of 0 to 1 according to their respective value ranges. and Then, through a comprehensive evaluation function The optimal operating frequency is determined, where σ is the root mean square deviation of the power density along the axial direction from the weight vector. The frequency corresponding to the minimum F value is the microwave excitation operating point of the main reaction cavity under the appropriate premixed liquid dielectric load. After the microwave excitation operating point is determined, the output power of the microwave source, the feed phase, and the insertion depth of the tuning screw in the rectangular waveguide section are adjusted in a coordinated manner.

[0038] Preferably, the output power is adjusted by incrementally increasing the anode current of the microwave source magnetron in small steps. The feed phase is scanned in segments between 0 and 2π by a phase shifter. The insertion depth of the tuning screw is driven by a stepper motor to advance and retreat in millimeter-level strokes. The three adjustment objects are updated cyclically in a preset order, which is recorded as one adjustment cycle. After each cycle, S11 and the power density distribution are reread.

[0039] For example, the microwave energy of the main reaction cavity here specifically refers to the microwave power density per unit volume within the effective working area of ​​the main reaction cavity, denoted as P, with units of W / cm³. The power density profile of the stable batch is derived from continuous sampling records of the coupling loss site P values ​​of historical qualified batches in the convergence state, and the upper and lower limits P are obtained by taking the 95% confidence interval for each batch. max With P min The typical value range is 0.8 to 1.6 W / cm³, and it fluctuates by ±10% depending on the dielectric load setting of the premixed liquid. When the P value at the coupling loss point falls back from the previous fluctuation range and remains below P for 30 seconds... min ,P max Within the range, when the drift amplitude per unit time is less than 0.05W / cm3, it is considered that the linkage adjustment has converged. At this time, the current output power, feed phase and tuning screw insertion depth readings are latched and archived as the adaptation working point of the microwave energy of the main reaction cavity under the dielectric load condition of the premixed liquid.

[0040] It is understood that the excitation intensity is not a single power value, but a multi-dimensional combination of power, phase and tuning parameters. Under the condition of premixed liquid dielectric load fluctuation, the microwave energy coupling of the main reaction cavity can be matched with the current dielectric state, avoiding local overexcitation or underexcitation in the coupling region caused by single external power compensation.

[0041] Step S103: Ignite the premixed liquid entering the main reaction chamber by adapting the excitation intensity of the dielectric load of the premixed liquid, and obtain the glow start delay time during the ignition process.

[0042] Based on the excitation intensity of the dielectric load of the adapted premixed liquid, microwave feeding ignition is performed on the premixed liquid entering the main reaction chamber. The start time of the excitation intensity being applied to the feed port is recorded to obtain the trigger start point of the ignition process. The glow emission signal of the premixed liquid is continuously acquired by a photodetector set in the observation window of the main reaction chamber. The moment when the glow emission signal first exceeds a preset glow intensity threshold is captured. The difference between this moment and the trigger start point of the ignition process is used to obtain the glow initiation delay time during the ignition process.

[0043] After the excitation intensity of the dielectric load of the adapted premixed liquid is formed, the microwave source of the main reaction cavity begins to output a microwave signal with a corresponding combination of power, phase, and tuning parameters to the feed port. In one embodiment, a synchronous trigger circuit is connected in series at the feed port. The synchronous trigger circuit generates a pulse signal at the instant when the rising edge of the microwave source output power crosses the start threshold. This pulse signal is entered into a timestamp register via a data acquisition card, and the recorded timestamp serves as the trigger start point t0 for the ignition process. The trigger start point is the unified time reference for subsequent glow delay measurements.

[0044] Specifically, a photodetector of the type of photomultiplier tube or silicon photodiode is arranged radially outside the quartz window of the main reaction chamber, and the incident light surface of the photodetector is aligned with the discharge volume of the premixed liquid in the microwave excitation region.

[0045] Preferably, a narrow-band optical filter is installed at the front end of the photodetector, and the filter parameters are determined according to the types of active free radicals in the premixed liquid. When the premixed liquid is a mixture of methane and air, the main active free radicals are CH and OH, whose characteristic emission lines are located at 431 nm and 309 nm, respectively. The center wavelength λ0 of the filter is aligned with the strongest emission line of the target free radical, where λ0 represents the wavelength corresponding to the peak transmittance of the filter, and the bandwidth is set to 10 to 20 nm, thereby filtering out the glow emission signal from the composite luminescence background in the cavity. The current output by the photodetector is converted into a voltage timing sequence by a transimpedance amplifier and then continuously acquired by the same data acquisition card at a sampling rate higher than the microwave period to obtain a point-by-point intensity sequence of the glow emission signal along the time axis.

[0046] It should be noted that the preset glow intensity threshold is determined by the glow start-up baseline under stable batch conditions. The start-up baseline is taken from several typical batches with stable glow start-up in the process history archive. The first jump amplitude of the glow emission signal after ignition is extracted from them, and the lower quartile is taken as the preset glow intensity threshold, thereby eliminating misjudgments of background noise and weak precursor fluctuations.

[0047] In one embodiment, the glow emission signal is scanned point by point along the time axis. When the intensity of three consecutive sampling points exceeds the preset glow intensity threshold at the same time, the timestamp corresponding to the first point that exceeds the threshold is recorded as the glow manifestation time t1. The difference between the glow manifestation time t1 and the trigger start point t0 of the ignition process is calculated, i.e., Δt = t1 - t0. The obtained Δt is the glow start delay time in this ignition process. The glow start delay time is defined as the time interval from the ignition trigger start point to the glow stabilization formation time, reflecting the microwave response characteristics of the premixed liquid under the current excitation intensity.

[0048] Step S104: Evaluate the glow start delay duration against a preset duration threshold. When the glow start delay duration exceeds the preset duration threshold, identify that glow start drift has occurred during the ignition process.

[0049] The glow discharge start-up delay duration is compared with a preset time threshold, which is set based on the upper limit of the glow discharge start-up delay duration under stable batch conditions, to obtain an over-limit indicator of the glow discharge start-up delay duration relative to the preset time threshold. Based on this over-limit indicator, if the glow discharge start-up delay duration exceeds the preset time threshold, the over-limit magnitude of the glow discharge start-up delay duration relative to the preset time threshold is characterized, and this over-limit magnitude is used as a measure of the drift degree to identify glow discharge start-up drift occurring in this ignition process.

[0050] Following the previously obtained glow discharge start-up delay duration Δt, which is the time interval from the ignition command to the glow formation time, this step compares the glow discharge start-up delay duration with a preset duration threshold Tth to evaluate the start-up status of the current ignition process. The preset duration threshold Tth is set based on the upper limit of the glow discharge start-up delay duration under stable batch conditions, and is usually taken as 1.2 to 1.5 times the maximum delay duration in the stable batch. For example, when the glow discharge start-up delay duration of the stable batch is distributed between 0.8 seconds and 1.2 seconds, the preset duration threshold Tth can be set to 1.5 seconds.

[0051] Specifically, several typical batches with stable glow discharge start-up and free radical generation levels within the expected range are selected from the process history archives. Glow discharge start-up delay duration samples of each batch are extracted, and the preset duration threshold Tth is set at 1.2 to 1.5 times the maximum glow discharge start-up delay duration in the stable batches. The setting of the preset duration threshold avoids including occasional high fluctuations in the normal window.

[0052] Specifically, the glow discharge start-up delay Δt for the current batch is obtained. This glow discharge start-up delay Δt is defined as the delay from the ignition command time t. start until the glow formation time t glow The time interval, i.e., Δt = t glow t start Subtracting Δt from the preset duration threshold Tth yields the difference ΔT = Δt. If ΔT ≤ 0, the over-limit flag is set to 0, indicating that the glow discharge start-up delay time falls within the normal window; if ΔT > 0, the over-limit flag is set to 1, and ΔT itself is used as the original record of the over-limit amplitude. The over-limit flag and the over-limit amplitude together constitute a binary description of the current ignition processing start-up state.

[0053] It should be noted that the characterization of the over-limit amplitude is not limited to the difference ΔT itself.

[0054] In one embodiment, ΔT is divided by the preset duration threshold Tth to obtain a dimensionless relative exceedance ratio. This relative exceedance ratio normalizes the baseline difference in glow discharge start-up delay between different process stages, facilitating cross-sectional comparison between adjacent batches. The exceedance amplitude serves as an objective measure of the degree of drift.

[0055] For example, when the over-limit flag is 1, it is determined that the current ignition process has deviated from the normal start-up range under the current excitation intensity. The larger the over-limit amplitude value, the higher the severity of the drift. Thus, it is identified that the current ignition process has experienced glow start drift, and the glow start drift serves as a trigger flag for subsequent field strength distribution pattern analysis.

[0056] Step S105: Extract the field strength distribution pattern during the discharge ignition process in the microwave excitation region when glow discharge drift occurs, analyze the field strength distribution pattern, and determine the reconstruction method of the discharge channel in the microwave excitation region.

[0057] When the glow discharge drift is identified, the amplitude and phase of the electric field vector at each probe node are synchronously recorded according to the pre-calibrated electric field probe grid's location in the microwave excitation region, thus obtaining the field strength distribution pattern during the discharge ignition process in the microwave excitation region. Based on the field strength distribution pattern, the amplitude gradient is extracted node by node along the axial and radial directions of the microwave excitation region, revealing the distribution of high-intensity dense regions and weak-field low-lying regions within the microwave excitation region. For the transition boundary between the high-intensity dense regions and the weak-field low-lying regions, the deviation path and deviation orientation of the discharge carriers are obtained. Based on the deviation path and deviation orientation, the expansion direction of the discharge channel cross-section is obtained based on the aggregation direction of the deviation path in the high-intensity dense region, and the contraction direction of the discharge channel cross-section is obtained based on the circumferential direction of the deviation path in the weak-field low-lying region. Combining the transition contour of the expansion and contraction directions along the axial direction of the microwave excitation region, the geometric reconstruction method of the discharge channel cross-section in the microwave excitation region is determined.

[0058] Following the previous identification of glow discharge initiation drift, which indicates that the discharge ignition behavior within the microwave excitation region deviates from the normal trend in the stable batch archives, initiation begins in-situ sampling and analysis of the electric field details at the moment of drift occurrence. In one embodiment, a set of directionally coupled electric field probe grids is arranged along the axial and radial directions of the microwave excitation region on the inner wall of the main reaction cavity. The electric field probe grid consists of several independent microprobes with their sampling surfaces facing the center of the discharge region, and is led out of the cavity through low-dielectric-loss coaxial feed lines.

[0059] Preferably, the probes are equidistantly distributed along the axial direction of the discharge zone, with an axial spacing of 25 mm to 40 mm between adjacent probes. They are arranged radially from the inner wall of the cavity towards the geometric center, with the spacing decreasing gradually. Near the inner wall, where the plasma gradient changes drastically, the probes are densely packed, with a radial spacing of 4 mm to 6 mm between adjacent probes. This spacing gradually decreases to 1 mm to 2 mm towards the geometric center, allowing for precise sampling of the discharge core. Before the cavity leaves the factory, all probes undergo individual calibration for sensitivity, zero-point drift, and response time under standard discharge conditions. The calibration data is uploaded to the recycled water monitoring terminal using the probe number as an index. This recycled water monitoring terminal is the upper-level monitoring unit responsible for water quality parameter acquisition, discharge state analysis, and process linkage control in this microwave discharge recycled water purification system. Its built-in shared archive provides a unified interface for calling calibration parameters for all probes within the cavity, supporting automatic real-time data correction and historical comparison during subsequent operation.

[0060] Specifically, each probe node simultaneously outputs a transient voltage waveform of the microwave electric field at the drift moment. This transient voltage waveform is first filtered by a low-pass filter and subjected to a diode envelope detector circuit to extract the amplitude envelope signal Ve. Then, it is sent together with the local oscillator reference signal into the quadrature demodulation channel to obtain the in-phase component I and the quadrature component Q, respectively. Based on this, the amplitude of the electric field vector E = k × (The phase φ = arctan(Q / I), where k is the probe calibration coefficient, determined by the probe response curve calibrated at the factory, with a typical value range of 0.85 to 1.15. The E and φ obtained from each node are filled into the sparse field strength space matrix according to the probe's three-dimensional spatial coordinates (x,y,z). A regular grid is established in the microwave excitation region with a grid step size of 5 mm. Three-dimensional kriging interpolation is used to densify the sparse node data. The amplitude channel is interpolated with linear weights, and the phase channel is interpolated after unwinding to avoid 2π jumps. Finally, it is unfolded in the three-dimensional coordinate system to form a continuous spatial amplitude field and phase field. The combination of the two is the field strength distribution pattern during the discharge ignition process in the microwave excitation region.)

[0061] It should be noted that the field strength distribution pattern not only describes the distribution of electric field amplitude but also includes the spatial fluctuations of phase orientation. Both together determine the direction of force and the tendency of motion of charged particles, forming the original base map for subsequent gradient analysis. Furthermore, the amplitude gradient is extracted node-by-node along the axial and radial directions of the microwave excitation region based on the field strength distribution pattern.

[0062] Specifically, the axial differential gradient Gz and radial differential gradient Gr are obtained by dividing the amplitude difference between adjacent probe nodes on the grid by the actual distance between the node and its neighbor. Along the axial direction, the distance between adjacent nodes is a constant value dz, which is directly used for normalization during calculation. Along the radial direction, since the probes are not equidistantly distributed according to progressive distances, the distance between the i-th node and the (i+1)-th node is denoted as dri. When calculating the radial gradient of the i-th node, dri is used as the divisor to normalize the amplitude difference to the rate of change per unit distance. The resulting gradient vector G is equal to the combination of Gz and Gr, reflecting the direction and rate of abrupt change in the electric field amplitude near the node. This local distance normalization method ensures the comparability of gradient values ​​at different locations.

[0063] In one embodiment, after normalizing the global field strength by peak value, node segments with normalized amplitude greater than 0.75 and gradient magnitude less than threshold T1 are grouped into high-intensity dense regions, and node segments with normalized amplitude less than 0.3 and gradient magnitude less than threshold T2 are grouped into weak-field low-lying regions. T1 is taken as 0.8 to 1.2 times the median gradient M, and T2 is taken as 0.5 to 0.9 times. In a specific example, when the calculated median gradient magnitude M is 50, T1 is taken as 45, and T2 is taken as 30.

[0064] It is understood that the high-intensity dense region represents the location where microwave energy is strongly concentrated locally, while the weak-field low-lying region corresponds to the location where microwave energy is not fully covered. These two types of regions are distributed alternately within the cavity. After normalizing the cavity field strength according to the peak value, locations with a normalized amplitude greater than 0.75 are classified as high-intensity dense regions, and locations with a normalized amplitude less than 0.3 are classified as weak-field low-lying regions. A node band exists between the high-intensity dense region and the weak-field low-lying region. This node band satisfies the condition that the normalized amplitude falls between 0.3 and 0.75, and the field strength gradient magnitude is greater than 1.5 times the average gradient magnitude of the entire region. This node band is the transition boundary between the two regions. The normal direction of the nodes is extracted along the transition boundary. The specific process is as follows: first, the field strength distribution E is obtained by sampling in the cavity at equal intervals; then, the partial derivatives gx, gy, and gz of each sampling point along the x, y, and z directions are calculated using central difference, and the gradient vector G = (gx, gy, gz) is synthesized, with a magnitude |G| = ; Select the sampling points that fall into the node zone as boundary nodes; For each boundary node, divide its gradient vector by the magnitude to complete the normalization. The resulting unit vector n=G / |G| is the normal direction of the node, which points from the weak field depression area to the high field density area.

[0065] It is understood that the normal direction refers to the direction of the normal to the isoelectric surface at the node, and this normal direction reflects the direction in which charged carriers are most easily accelerated and migrated under the influence of the electric field. Path construction adopts the gradient tracing method: starting from the node with the maximum field strength, the next adjacent node with the second highest field strength and a distance of less than 0.5 mm is searched along the normal direction of the current node as the next connection point. This process is repeated until a node or boundary node with a field strength lower than 10% of the initial field strength is reached. Each node is connected in sequence to obtain the actual deviation path of the discharged carriers in the field strength distribution pattern. The path nodes are naturally arranged from high to low field strength.

[0066] For example, the actual deviation path is compared node by node with the normal path of the discharge carriers in the stable batch file. The orientation of the line connecting the nodes with the largest deviation is the deviation orientation, which is recorded in the form of azimuth angle, thus providing an objective characterization of the direction of the drift in space. Further, regarding the aggregation direction of the deviation path in the high-density region, the expansion direction of the discharge channel cross-section in that segment is calculated along the intrusion depth and node density of the deviation path in the high-density region, with the expansion direction pointing towards the center of the high-density region; regarding the bypassing direction of the deviation path in the weak-field low-lying region, the retraction direction of the discharge channel cross-section in that segment is calculated along the avoidance arc of the deviation path in the weak-field low-lying region, with the retraction direction away from the center of the weak-field low-lying region.

[0067] Specifically, within the microwave excitation region, the cross-sectional profile of the discharge channel exhibits periodic expansion and contraction as its axial position changes. For each cross-sectional position along the axial direction of the microwave excitation region, the point with the maximum radial dimension of the discharge channel profile is extracted as the feature point in the expansion direction, and the point with the minimum radial dimension is extracted as the feature point in the contraction direction. The expansion direction feature points of adjacent cross-sections are connected sequentially to form the expansion direction profile line; the contraction direction feature points of adjacent cross-sections are connected sequentially to form the contraction direction profile line. By connecting the beginning and end of the expansion direction profile line and the contraction direction profile line, a continuous transition profile of the discharge channel along the axial direction is formed.

[0068] In one embodiment, the continuous transition profile is fitted into a smooth curve in the axial direction using spline interpolation. This curve satisfies the second-order continuous differentiability condition, thereby obtaining the geometric orientation of the discharge channel cross-section from the inlet to the outlet within the microwave excitation region.

[0069] It is understood that the aforementioned cross-sectional geometry reconstruction method refers to the cross-sectional geometry adjustment scheme of the discharge channel in the microwave excitation region, which is output as the cross-sectional centroid trajectory and the cross-sectional boundary parameterization function. The cross-sectional boundary parameterization function is in polar coordinate form: r = f(θ, a1, a2, ..., a...). n ) represents the boundary contour, r is the radial distance, θ is the polar angle, and a1 to a nThe coefficient parameters are used to control the boundary shape. The dielectric load of the premixed liquid is defined as the equivalent dielectric constant ε per unit volume of the premixed liquid. The product ε with the local electric field intensity E E. By collecting the electric field intensity distribution in real time through 3 to 5 electric field probes arranged in the discharge region, and combining this with the dielectric constant test value of the premixed liquid, the spatial distribution of the dielectric load is calculated. The cross-sectional geometry reconstruction method serves as the input basis for subsequent discharge excitation pattern adjustment actions, enabling the cross-sectional shape and boundary position of the discharge channel to dynamically match the current dielectric load distribution, ensuring that the actual field intensity distribution in the discharge region is compatible with the dielectric properties of the premixed liquid.

[0070] Step S106: Adjust the cross-sectional geometry of the discharge channel inside the microwave excitation region according to the reconstruction method of the discharge channel in the microwave excitation region to form a discharge excitation pattern that adapts to the dielectric properties of the premixed liquid.

[0071] Based on the cross-sectional geometry reconstruction method of the discharge channel in the microwave excitation region, the target cross-sectional center offset, the ratio of the major and minor axes of the target cross-section, and the position of the target boundary inflection point are extracted for each segment along the axial direction of the discharge channel to obtain the adjustment target vector of the discharge channel cross-sectional geometry. According to the adjustment target vector, the cavity constraint, magnetic constraint coil, and airflow deflector plate in the microwave excitation region are driven in a coordinated manner. The cavity constraint, magnetic constraint coil, and airflow deflector plate perform radial displacement, axial magnetic flux gradient adjustment, and deflection angle switching respectively based on the target cross-sectional center offset, the ratio of the major and minor axes of the target cross-section, and the position of the target boundary inflection point, to obtain the actual cross-sectional geometry of the discharge channel in the microwave excitation region. Based on the spatial correspondence between the actual cross-sectional geometry and the dielectric properties of the premixed liquid in the reconstructed channel, the uniform distribution of the electric field intensity along the cross-section of the discharge channel and the continuous absorption direction of the microwave energy along the axial direction are obtained, forming a discharge excitation pattern adapted to the dielectric properties of the premixed liquid.

[0072] Following the previously determined method for reconstructing the cross-sectional geometry of the microwave excitation region discharge channel, this step further transforms the geometric parameters in the cross-sectional geometry reconstruction method into drivable adjustable quantities. Through the coordinated action of multiple adjustable components within the cavity, the discharge channel ultimately conforms to the reconstructed contour in physical space, forming a discharge excitation pattern that matches the dielectric properties of the premixed liquid. In one embodiment, the discharge channel is uniformly divided into several segments along the axial direction of the microwave excitation region, with each segment corresponding to a cross-sectional slice. For each cross-sectional slice, three types of parameters are read from the cross-sectional geometry reconstruction method: the target cross-sectional center offset Δr, representing the lateral offset distance of the centroid of the cross-section relative to the initial axis of the discharge channel; the target cross-sectional major-minor axis ratio k, representing the scaling ratio of the cross-section in the major axis direction and the minor axis direction, used to characterize the degree of deformation of the cross-section from a near-circular shape to an elliptical shape; and the target boundary inflection point position θp, representing the azimuth angle along the circumferential direction of the curvature abrupt change point on the boundary curve of the cross-section. These three types of parameters constitute the adjustment description of a single segment.

[0073] Specifically, the three types of parameters of all segments are arranged and spliced ​​in axial order to form the adjustment target vector of the discharge channel cross-sectional geometry. The adjustment target vector is output to the drive module of the subsequent adjustment component using the segment number as an index.

[0074] It should be noted that the cavity constraint is a set of radially expandable dielectric blocks installed on the inner wall of the microwave excitation region. Each dielectric block corresponds to an axial segment and is driven radially forward and backward by a stepper motor via a lead screw mechanism. The expansion and contraction of the dielectric block changes the effective cross-sectional area distribution of the cavity in that segment, causing the region of maximum microwave electric field intensity to shift radially. The specific mechanism is as follows: when the dielectric block extends towards the center of the cavity, the electromagnetic field boundary conditions of that segment change, the distribution of the standing wave field formed by microwaves in the cavity is adjusted, and the area of ​​concentrated electric field energy shifts to the opposite side of the dielectric block by 0.5 mm to 3 mm, thereby driving the plasma discharge region to move radially to a new peak electric field intensity position. By adjusting the expansion and contraction of the dielectric blocks in different axial segments, the three-dimensional position control of the discharge region in the radial and axial directions can be achieved, keeping the relative position of the discharge region and the surface of the material to be treated within a set range.

[0075] In one embodiment, for each segment's target cross-sectional center offset Δr, the lead screw output displacement corresponding to each pulse of the stepper motor is δ=L×θ / 360=1×1.8 / 360≈0.005 mm; the drive module calculates the required number of pulses N according to N=Δr / δ=Δr×360 / (L×θ) and sends it to the corresponding stepper motor, where N is the number of pulses, L is the lead screw lead of 1 mm, and θ is the step angle of 1.8 degrees. The stepper motor drives the lead screw to push the dielectric block of that segment radially, so that its radial offset reaches Δr, thereby realizing the segment-by-segment repositioning of the cavity constraint component to the centroid of the cross-section. The geometric axis of the magnetic constraint coil is arranged to coincide with the central axis of the microwave excitation region, and is composed of several independently adjustable solenoid units connected in series along the axial direction. Each solenoid unit corresponds to an axial segment, and its excitation current is individually controlled by the constant current source of the corresponding channel.

[0076] It is understandable that adjusting the excitation current of the solenoid unit can change the axial magnetic field strength of that segment. The axial magnetic field exerts Lorentz constraint on the charged carriers, and the difference in magnetic field strength in the major and minor axis directions determines the scaling of the major and minor axis ratio of the discharge cross section.

[0077] In one embodiment, for each segment's target cross-sectional major-minor axis ratio k, this ratio is converted into the current difference between the corresponding solenoid unit and its adjacent units. The constant current source adjusts its output according to this current difference, causing the magnetic confinement coil to form a magnetic flux intensity gradient along the axial direction, thereby completing the segment-by-segment adjustment of the magnetic confinement coil's cross-sectional major-minor axis ratio. The airflow deflector plate is located at the front end of the premixed liquid mist entering the microwave excitation zone, and is composed of several fan-shaped thin blades, evenly distributed along the circumference of the discharge channel and rotating around a radial hinge. Further, each fan-shaped thin blade corresponds to an azimuth sector on the discharge cross-sectional boundary. The deflection angle of the fan-shaped thin blade determines the incident direction of the premixed liquid mist in that sector, thereby affecting the discharge boundary morphology at that azimuth. For each segment's target boundary inflection point position θp, the drive module issues a deflection command to the corresponding fan-shaped thin blade according to the azimuth sector mapping relationship. The fan-shaped thin blade switches to the target deflection angle through the servo motor at its root, causing the airflow deflector plate to stabilize the boundary inflection point at the azimuth position θp.

[0078] For example, the channel is divided into several segments with a length of 20 mm along the axial direction of the microwave excitation region. A local coordinate system is established for each segment with the intersection of the axis of the excitation region and the cross section of the segment as the reference point. The three types of actions are applied synchronously and superimposed segment by segment according to the following rules: The radial displacement d of the cavity constraint directly determines the offset vector of the centroid of the discharge channel cross section relative to the reference point, with a displacement range of 0 to 3 mm; The axial magnetic flux gradient g of the magnetic confinement coil is mapped to the cross section length-to-minor axis ratio k through the plasma radial contraction ratio, k = 1 + a·g, where g is the axial magnetic flux gradient (unit T / m), and a is the contraction coefficient (unit m / T) obtained from the calibration test, with a value of 0.15 to 0.25 m / T, making a·g a dimensionless quantity; The deflection angle θ of the airflow deflector plate determines the angular position of the inflection point of the cross section boundary relative to the major axis. Each time the deflection angle is switched, the inflection point position deflects circumferentially by an amount equal to θ. The superposition mechanism of the three types of actions is achieved by decoupling the geometric parameters. First, the centroid is translated by 'd', then the major and minor axes are stretched by 'k', and finally the inflection point is located by 'θ', closing the boundary with a spline curve to obtain the actual cross-sectional profile of that segment. By sequentially splicing the profiles of each segment along the axial direction, the actual cross-sectional geometry of the discharge channel from the inlet to the outlet in the microwave excitation region is obtained. For example, for a segment with d=1.2mm, g=0.8T / m, and θ=30°, the centroid shift is 1.2mm, the major-to-minor axis ratio is approximately 1.16, and the inflection point is located 30° clockwise from the major axis. Furthermore, the actual cross-sectional geometry is compared point-to-point with the spatial distribution of the premixed liquid's dielectric properties within the reconstructed channel.

[0079] Specifically, the premixed liquid exhibits different dielectric constants and loss tangents along the axial direction within the discharge channel, which has been segmented and its geometric parameters adjusted. The matching verification process first measures the dielectric constant εr and loss tangent tanδ of each segment using a vector network analyzer. Then, a three-dimensional model of the corresponding segment is established in electromagnetic field simulation software. The measured dielectric parameters and geometric parameters such as the radius r and wall thickness t of the current cross-section are input to calculate the electric field intensity distribution E and axial power flux density S of that segment's cross-section. When the ratio of the standard deviation σE of the electric field intensity within the cross-section to the average value Eavg exceeds 0.15, the channel radius of that segment is adjusted to make the field intensity distribution more uniform; at this point, the cross-section is considered to have achieved a uniform distribution. To verify the axial continuous absorption direction, the power gradient between adjacent segments i and i+1 is calculated, which is the difference between Si+1 and Si divided by the two segment spacing Δz. When the absolute value of this gradient exceeds 0.08 watts per square millimeter, the dielectric or geometric parameters of segment i+1 need to be adjusted so that the power transition gradient is controlled within 0.08 watts per square millimeter, ensuring that the microwave energy is absorbed smoothly along the axial direction without abrupt changes.

[0080] It is understood that the spatial superposition of the uniform distribution and the continuous absorption direction constitutes a discharge excitation pattern adapted to the dielectric properties of the premixed liquid. The discharge excitation pattern is output in the form of a set of cross-sectional morphology parameters and an axial power distribution curve, which serves as the control basis for the subsequent generation process of active free radicals, thereby ensuring that the discharge process remains spatially uniform and axially continuous under the dielectric fluctuation conditions of the premixed liquid.

[0081] Step S107: Control the generation process of active free radicals through the discharge excitation pattern to obtain the expected level of active free radical generation and suppress abrupt changes in the generation of active free radicals.

[0082] By applying a uniform field strength and continuous absorption direction to the discharge channel within the microwave excitation region using a discharge excitation pattern adapted to the dielectric properties of the premixed liquid, the dissociation and collision activity of the premixed liquid molecules are obtained, determining the generation process of active free radicals and their instantaneous generation rate and cumulative generation level. The intensity of characteristic emission lines of the active free radicals is collected in real time using an emission spectrometer located at the outlet section of the main reaction cavity. Based on these characteristic emission line intensities, a measured sequence of the instantaneous generation rate and cumulative generation level of the active free radicals is obtained. This measured sequence is compared with the expected generation level to obtain the generation level deviation and generation rate fluctuation amplitude. Based on the generation level deviation and generation rate fluctuation amplitude, the cross-sectional morphology parameter set and axial power distribution curve in the discharge excitation pattern are fine-tuned to bring the instantaneous generation rate back to the expected allowable band, suppressing abrupt jumps in the generation of active free radicals and obtaining the expected active free radical generation level.

[0083] Following the discharge excitation pattern adapted to the dielectric properties of the premixed liquid established in the previous step, this section physically applies the discharge excitation pattern to the microwave excitation region of the main reaction cavity, and performs experimental measurement and loop correction on the generated active free radicals to maintain their generation level stable within the expected range. In one embodiment, the discharge excitation pattern is stored in the main reaction cavity control terminal in the form of two types of data: cross-sectional shape parameter set and axial power distribution curve. The control terminal drives the cavity constraint, magnetic constraint coil, and airflow deflector plate to maintain the current cross-sectional geometry according to the cross-sectional shape parameter set, and sends segment-by-segment power commands to the microwave source according to the axial power distribution curve.

[0084] Specifically, the power setting for each segment ensures that each cross-sectional slice within the microwave excitation region receives microwave power matched to its dielectric load, where the dielectric load is defined as the dielectric loss power density of the premixed liquid vapor per unit volume, measured in watts per cubic centimeter. Power matching is achieved by real-time monitoring of the imaginary part of the complex permittivity of each slice. And electric field strength E, according to Calculate the required power; power loss is determined by the imaginary part. The value is determined by f, where f is the microwave frequency and ε0 is the vacuum permittivity. E represents the imaginary part of the complex permittivity. rms This is the effective value of the electric field intensity; if the peak electric field E is taken as... peak Substituting the values, the formula becomes P = π·f·ε0· ·E peak ² (i.e., including a 1 / 2 factor) enables adaptive adjustment of the power of each slice. Multiple slices together form a uniform field strength distribution along the cross-section of the discharge channel and a microwave absorption direction that transitions continuously along the axial direction. Under the action of the uniform field strength, the premixed liquid molecules are accelerated by electron collisions and dissociate. The dissociated fragments further collide with background neutral particles, which mainly originate from vapor molecules formed by the evaporation of the premixed liquid and inert carrier gases such as argon or nitrogen introduced into the plasma environment. The degree of dissociation and collision activity of the premixed liquid molecules are determined through the collision process.

[0085] It is understood that the degree of dissociation corresponds to the number of chemical bonds that are broken in the premixed liquid molecules per unit volume, and the collision activity corresponds to the effective probability of generating new free radicals through secondary collisions. The two are superimposed segment by segment along the discharge channel axis to constitute the generation process of active free radicals. The generation process includes two core data: instantaneous generation rate and cumulative generation level.

[0086] In one embodiment, a quartz observation window is radially opened at the outlet section of the main reaction chamber, and a broadband emission spectrometer (hereinafter referred to as the spectrometer) is installed outside the quartz observation window. The spectrometer uses a diffraction grating to spread the composite emission of the plasma in the outlet section according to wavelength.

[0087] Preferably, a separate narrowband channel is set for the characteristic emission spectra of active free radicals of interest in the resin removal process. These active free radicals include oxygen and hydrogen free radicals. The center wavelength of the channel is aligned with the transition lines of the active free radicals, with oxygen free radicals aligned to a wavelength of 777 nm and hydrogen free radicals aligned to a wavelength of 656 nm. The spectral intensity is sampled by an internal photomultiplier tube at 1 to 10 millisecond cycles. The intensity of the characteristic emission spectrum is linearly related to the free radical concentration in the low self-absorption range. Using an intensity-concentration correspondence table recorded beforehand in a calibration batch, the intensity of the characteristic emission spectrum sampled in each cycle is directly converted to the active free radical concentration at the outlet. The calibration batch refers to a spectral intensity calibration experiment conducted using a standard gas of known concentration during stable operation of the plasma reactor at set power, gas flow rate, and chamber pressure. The outlet flow rate Q is measured in real time by a mass flow meter installed at the outlet. Combined with the active free radical concentration C at the outlet, the instantaneous generation rate R = C × Q of the active free radicals is calculated. The instantaneous generation rates of all cycles are arranged in chronological order of sampling time to form a measured sequence. The cumulative measured level is obtained by integrating the measured sequence over time.

[0088] Specifically, the expected generation level stored at the control terminal is an ideal time-series curve calculated through offline simulation, and the target values ​​at each moment are recorded with a sampling interval of 1 second. The measured sequence is subtracted from the expected generation level moment by moment along the same time axis, and the resulting difference Δ is the generation level deviation, where Δ = measured value. Expected value. Simultaneously, a 30-second sliding time window and a 5-second sliding step size are used to scan the instantaneous generation rate. The difference between the maximum and minimum values ​​within the window is taken as the generation rate fluctuation amplitude A, i.e., A = peak value within the window. Valley value within the window. Further, based on the generation level deviation Δ and the generation rate fluctuation amplitude A, a loop fine-tuning is performed on the field strength distribution parameters of each radial region in the discharge excitation pattern and the power density distribution coefficient along the axial direction: when Δ exceeds ±3% of the rated value, the cross-sectional absorption characteristics are changed by adjusting the radial extension of each segment cavity constraint; when A exceeds 1.5 times the rated fluctuation, the power gradient is smoothed by optimizing the axial segment-by-segment power distribution, thus achieving dual constraints on the generation level and rate stability.

[0089] In one embodiment, the loop fine-tuning adopts the proportional-integral control principle: when the deviation is positive and exceeds the upper limit of the expected allowable band, the axial power distribution curve is raised by one level, with each level corresponding to a 5% increase in power density; when the deviation is negative and exceeds the lower limit of the expected allowable band, it is lowered by one level, with each level corresponding to a 5% decrease in power density; when the generation rate fluctuation amplitude A exceeds 1.5 times the rated fluctuation amplitude of the stable batch, a smoothing passivation correction is performed on the cross-sectional morphological parameter set, which includes three parameters: the ratio of the major and minor axes of the axial cross-section of the reaction cavity, the position of the boundary inflection point, and the radius of curvature. The smoothing passivation correction specifically involves taking the arithmetic mean of the morphological parameters of two adjacent power distribution segments along the axial direction as the transition value, wherein the axial segments are divided into 10 mm intervals. This smooth transition reduces the sharp changes in the plasma diffusion path.

[0090] For example, the expected tolerance band is determined by the upper and lower envelopes of the instantaneous generation rate under a stable batch, and the preset fluctuation threshold is determined by the upper limit of the rate fluctuation amplitude under a stable batch. The loopback fine-tuning continues until the instantaneous generation rate falls back into the expected tolerance band.

[0091] Understandably, since the loop fine-tuning is designed to suppress chain disturbances caused by random drift of the premixed liquid's dielectric constant, after the aforementioned closed-loop parameter correction, the peak-to-valley difference of the instantaneous generation rate converges by more than 60% compared to the uninterrupted condition. The rate mutation amplitude within a single cycle is limited to the set sliding window threshold of ±5%, thus suppressing abrupt jumps in the generation of active free radicals. The relative deviation e between the cumulative generation amount and the expected generation curve remains within the allowable range of ±3%, where e = (actual cumulative amount - expected cumulative amount) / expected cumulative amount. Stability is determined when no over-limit alarm is triggered within 10 consecutive sampling cycles. Therefore, even when the premixed liquid's dielectric constant ε exhibits random fluctuations within the range of ±8%, the resin removal operation can still maintain a stable output of active free radicals.

[0092] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the generation of active free radicals during microwave plasma resin removal, characterized in that, The method includes: The concentration of soluble decomposition products in the recycled water is obtained, the dielectric properties of the premixed liquid in the microwave band are identified, and the dielectric properties are evaluated to ensure their compatibility with a preset dielectric threshold. If the dielectric properties exceed the preset dielectric threshold, the dielectric properties of the premixed liquid are analyzed to obtain the microwave energy of the main reaction cavity. The microwave energy of the main reaction cavity is then adjusted to obtain the excitation intensity that matches the dielectric load of the premixed liquid. The premixed liquid entering the main reaction chamber is ignited by adapting the excitation intensity of the dielectric load of the premixed liquid, and the glow start delay time during the ignition process is obtained. The glow start delay time is evaluated against a preset time threshold. When the glow start delay time exceeds the preset time threshold, glow start drift is determined to have occurred during the ignition process. When glow discharge drift occurs during ignition, the field strength distribution pattern in the microwave excitation region during the discharge ignition process is extracted, and the field strength distribution pattern is analyzed to determine the reconstruction method of the discharge channel in the microwave excitation region. Adjust the cross-sectional geometry of the discharge channel inside the microwave excitation region according to the reconstruction method of the discharge channel in the microwave excitation region to form a discharge excitation pattern that adapts to the dielectric properties of the premixed liquid. By controlling the generation process of active free radicals through the discharge excitation pattern, the expected level of active free radical generation can be obtained, and abrupt jumps in the generation of active free radicals can be suppressed.

2. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The process of obtaining the concentration of soluble decomposable substances in the recycled water and identifying the dielectric properties of the premixed solution in the microwave band includes: Continuous sampling and monitoring of the recycled water are conducted to obtain the concentration values ​​of soluble decomposable substances in the recycled water. The concentration values ​​are compared with the baseline reference values ​​of the recycled water to obtain the concentration deviation of soluble decomposable substances and determine the compositional fluctuation characteristics of the premixed liquid input side. Based on the composition fluctuation characteristics, the dielectric constant and loss tangent of the premixed liquid are measured by frequency sweep in the microwave operating frequency band to obtain the dielectric response curves of the premixed liquid at different decomposition product concentrations. The current dielectric property parameters of the premixed liquid are determined based on the dielectric response curves.

3. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The adaptation evaluation of the dielectric properties and the preset dielectric threshold includes: The current dielectric properties of the premixed liquid are compared with the preset dielectric threshold range to obtain the deviation of the dielectric properties relative to the threshold range. If the deviation exceeds the threshold range, it is determined that the dielectric properties of the premixed liquid in the microwave frequency band have exceeded the limit, and an adaptation evaluation conclusion for the dielectric state of the premixed liquid is obtained.

4. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, If the dielectric properties exceed a preset dielectric threshold, the dielectric properties of the premixed liquid are analyzed to obtain the microwave energy of the main reaction cavity. The microwave energy of the main reaction cavity is then adjusted to obtain an excitation intensity suitable for the dielectric load of the premixed liquid, including: Based on the normalized distance between the real part of the complex permittivity and the loss tangent exceeding the upper and lower limits of the threshold, the polarization loss variation and microwave energy absorption load magnitude of the premixed liquid are obtained. Combining the cumulative distribution of the variation and load magnitude in the coupling region of the main reaction cavity, the microwave energy supply of the main reaction cavity is obtained. The reflection coefficient and transmission coefficient of the microwave feed port of the main reaction cavity are scanned and measured according to the microwave energy supply to determine the microwave excitation operating point of the main reaction cavity. The output power and feed phase of the microwave source, as well as the insertion depth of the tuning screw of the rectangular waveguide section, are adjusted in conjunction with the microwave excitation operating point. The convergence is determined by the power density at the coupling loss point falling back to the preset power threshold range, thus obtaining the excitation intensity of the premixed liquid dielectric load.

5. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The step of igniting the premixed liquid entering the main reaction chamber by adapting the excitation intensity to the dielectric load of the premixed liquid, and obtaining the glow discharge delay time during the ignition process, includes: Microwave-feed ignition is performed on the premixed liquid entering the main reaction chamber, and the start time of the excitation intensity at the feed port is recorded to obtain the triggering point of the ignition process. The glow emission signal of the premixed liquid is continuously collected by a photodetector installed in the observation window of the main reaction chamber. The moment when the glow emission signal first exceeds the preset glow intensity threshold is captured. The difference between the moment and the triggering start point of the ignition process is calculated to obtain the glow start delay time.

6. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The evaluation of the glow start delay duration and a preset time threshold, and the identification of glow start drift in the ignition process when the glow start delay duration exceeds the preset time threshold, includes: The glow discharge start-up delay duration is compared with a preset duration threshold, which is set based on the upper limit of the glow discharge start-up delay duration under stable batch conditions, to obtain an over-limit indicator of the glow discharge start-up delay duration relative to the preset duration threshold; Based on the over-limit indicator, the over-limit amplitude is characterized, and the over-limit amplitude is used as a measure of the drift degree to identify the glow start drift that occurred during this ignition process.

7. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The electric field distribution pattern during the discharge ignition process in the microwave excitation region during glow discharge start-up drift is extracted, and the electric field distribution pattern is analyzed to determine the reconstruction method of the discharge channel in the microwave excitation region, including: Based on the pre-calibrated electric field probe grid's location in the microwave excitation region, the amplitude and phase of the electric field vector at each probe node are recorded synchronously to obtain the field strength distribution pattern. The amplitude gradient is extracted node by node along the axial and radial directions of the microwave excitation region to obtain the distribution of high-intensity dense region and weak-field low-lying region in the microwave excitation region. For the transition boundary between the high-intensity dense region and the weak-field low-lying region, the deviation path and deviation direction of the discharge carriers are obtained. Based on the deviation path and the deviation orientation, the expansion direction of the discharge channel cross-section is obtained by considering the aggregation direction of the deviation path in the high-intensity dense region, and the retraction direction of the discharge channel cross-section is obtained by considering the bypass direction of the deviation path in the weak-field low-lying region. Combining the transition contour of the expansion direction and the retraction direction along the axial direction of the microwave excitation region, the cross-sectional geometric reconstruction method of the discharge channel in the microwave excitation region is determined.

8. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The step of adjusting the cross-sectional geometry of the discharge channel within the microwave excitation region according to the reconstruction method of the discharge channel in the microwave excitation region to form a discharge excitation pattern adapted to the dielectric properties of the premixed liquid includes: The target cross-sectional center offset and the ratio of the major and minor axes of the target cross-section to the inflection point of the target boundary are extracted from each segment along the axial direction of the discharge channel to obtain the target vector for adjusting the geometry of the discharge channel cross-section. Based on the adjustment target vector, the cavity constraint component and magnetic constraint coil in the microwave excitation region are driven in a linkage with the airflow deflector plate to obtain the actual cross-sectional geometry of the discharge channel in the microwave excitation region. Based on the spatial correspondence between the actual cross-sectional geometry and the dielectric properties of the premixed liquid in the reconstructed channel, the uniform distribution of electric field intensity along the cross-section of the discharge channel and the continuous absorption direction of microwave energy along the axial direction are obtained, forming a discharge excitation pattern adapted to the dielectric properties of the premixed liquid.

9. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 1, characterized in that, The method of controlling the generation process of reactive free radicals through the discharge excitation pattern to obtain the expected level of reactive free radical generation and suppress abrupt jumps in the generation of reactive free radicals includes: By applying a uniform field strength and continuous absorption direction to the discharge channel in the microwave excitation region using the discharge excitation pattern adapted to the dielectric properties of the premixed liquid, the dissociation and collision activity of the premixed liquid molecules are obtained, and the generation process of active free radicals, as well as their instantaneous generation rate and cumulative generation level, are determined.

10. The method for controlling the generation of active free radicals during microwave plasma resin removal according to claim 9, characterized in that, The determination of the generation process of active free radicals and their instantaneous generation rate and cumulative generation level includes: The intensity of characteristic emission lines of active free radicals is collected in real time by an emission spectrometer set at the outlet section of the main reaction chamber. The measured sequence of instantaneous generation rate and cumulative generation level of the active free radicals is obtained based on the intensity of the characteristic emission lines. The measured sequence is compared with the expected generation level to obtain the generation level deviation and generation rate fluctuation amplitude. Based on the deviation of the generation level and the fluctuation amplitude of the generation rate, the cross-sectional morphology parameter set and axial power distribution curve in the discharge excitation pattern are finely adjusted in a loop to bring the instantaneous generation rate back to the expected allowable band, suppress the sudden jump in the generation of active free radicals, and obtain the expected level of active free radical generation.

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