A method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model

Abstract

This invention relates to the field of online detection technology for liquid-phase organic matter, and particularly to a method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model. The method involves first filtering and stabilizing the organic stock solution and deionized water separately, then mixing them at an adjustable volume ratio using a proportional volumetric pump to prepare a mixed test solution. Simultaneously, three parameters—volume ratio, pH value, and conductivity value—are collected and input into an offline-calibrated volume ratio-conductivity-pH compensation model to calculate the true acidity of the organic stock solution. The volume ratio is used as an independent variable to correct for dilution-induced deviations in ion activity and dielectric environment. This invention employs three-parameter coupled correction, enabling high-precision, universal online quantitative detection of non-buffered, weakly polar organic stock solutions with conductivity below 100 μS / cm. It is equipped with online sensor calibration, anomaly warning, and confidence-driven adaptive ratio control functions, achieving full automation and adaptability for continuous online monitoring of various organic materials such as alcohols, ketones, esters, and alkanes.

Description

Technical Field

[0001] This invention relates to the field of online detection technology for liquid-phase organic matter, and particularly to a method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model. Specifically, it relates to an automated online quantitative detection technology for the acidity of non-aqueous organic systems with low ionic strength and low conductivity. In particular, it provides a fully automated online acidity analysis method based on a multi-parameter coupled mathematical compensation model of volume ratio, solution conductivity, and pH, specifically for the online accurate characterization of trace organic acid content in weakly polar organic raw materials under continuous production conditions such as esterification, solvent synthesis, and fine chemical processes. Background Technology

[0002] In industrial production fields such as chemical, pharmaceutical, food, and energy, the acidity index of liquid-phase organic materials such as alcohols, ketones, esters, and hydrocarbons is a core process parameter for evaluating product quality, monitoring organic reaction processes, and predicting equipment corrosion risks. Achieving rapid, accurate, and continuous online monitoring of the acidity of liquid-phase organic materials has significant engineering value for closed-loop process control and production safety management.

[0003] Currently, the mainstream technology for online detection of acidity of liquid organic matter in industrial settings is the direct pH measurement method based on fixed-ratio dilution: the organic stock solution to be tested is diluted and mixed with deionized water at a fixed preset volume ratio, and the pH of the mixture is measured using a conventional pH electrode. This pH value is then used to characterize the acidity of the organic stock solution. This detection method has inherent flaws in both its theoretical mechanism and practical engineering applications, as detailed below.

[0004] First, there is no direct linear correlation between the pH of the diluted mixture and the actual acidity of the organic stock solution, resulting in nonlinear distortion in the measured values. The organic solvent system has extremely low ion content and low conductivity, and its dielectric constant differs significantly from that of pure water, causing a clear difference in ion activity coefficients between the system and the aqueous phase. Adding deionized water to dilute the organic stock solution causes drastic nonlinear changes in the system's ionic strength and dielectric environment. The pH of the mixed solution and the actual acidity (hydrogen ion concentration, total acid value) of the organic stock solution exhibit a complex nonlinear mapping relationship, making it impossible to accurately deduce the actual organic acid content of the stock solution from the pH of the mixed solution through simple conversion. This ultimately leads to a significant deviation in the quantitative detection results. Taking the esterification reaction organic feed solution as an example, relying solely on the pH of the diluted mixture cannot accurately convert the actual carboxylic acid concentration of the stock solution, rendering quantitative detection ineffective.

[0005] Second, existing detection methods have poor media adaptability and are difficult to adapt to flexible continuous production conditions involving multiple product categories. The dilution ratio-pH empirical correlation model established by this method is highly bound to the inherent physicochemical properties of the corresponding organic solvent, such as polarity and dielectric constant. The dilution-pH correspondence obtained for the methanol system cannot be directly reused for other organic materials such as acetone and ethyl acetate. After changing the production materials, multiple batches of offline calibration and reconstruction of empirical correlation curves must be carried out again. The process is cumbersome, and the downtime and debugging cycle is long, making it unsuitable for flexible chemical production lines that produce multiple products alternately.

[0006] Third, the lack of dynamic calibration makes it difficult to guarantee detection accuracy under low conductivity conditions. Conventional pH electrodes are prone to response lag, reading drift, and measurement inaccuracies in low-conductivity organic-water mixtures. This phenomenon stems from the continuous fluctuation of the liquid junction potential of the reference electrode. Traditional direct pH measurement schemes using proportional dilution only collect a single pH detection signal and do not incorporate conductivity parameters (conductivity can characterize the total ion concentration and ionic strength of the solution in real time and online), which is a core characteristic parameter for correcting pH measurement deviations in low-conductivity environments. Due to the lack of conductivity calibration, existing detection systems cannot identify abnormal operating states of pH electrodes under low ionic strength conditions, nor can they effectively compensate for system measurement errors caused by electrode drift.

[0007] To address the aforementioned technical deficiencies, several improved detection schemes have been disclosed in the existing technology, but none of them have eliminated the core measurement deviation from the underlying mechanism, and the technical improvements have obvious limitations.

[0008] Chinese patent CN206193015U discloses an online monitoring device for branch sampling and static / dynamic mixing followed by pH detection of the mixed solution. This solution only automates the sampling, mixing, and detection process. The core detection logic is still to directly measure the pH after dilution. It does not solve the problem of nonlinear conversion between the pH of the mixed solution and the true acidity of the organic stock solution. At the same time, it cannot eliminate the measurement deviation caused by the difference in solvent medium, and the media versatility is insufficient.

[0009] Chinese invention patent application CN114487028A discloses a technical solution to stabilize pH measurement results by adding inorganic salt ionic strength regulators such as potassium chloride to water samples with low conductivity. This solution introduces exogenous electrolytes into the system to be tested, which will change the original chemical balance of the organic raw liquid and cause impurity contamination to high-purity organic materials. It is not suitable for quantitative detection of acidity of high-purity organic liquids in fine chemicals and pharmaceuticals.

[0010] Chinese patent CN122084724A discloses a technical approach to construct a feature vector by integrating multiple variables such as temperature and solvent concentration to achieve measurement compensation. The input variables of this scheme include indirect process parameters such as solvent concentration, which need to be acquired externally by the DCS control system. The parameter acquisition has poor real-time performance and is prone to introducing additional measurement errors. More importantly, this technology does not include the online real-time measurable conductivity as a core correction parameter in the model, nor does it include the controllable and real-time readable volume ratio as an independent input variable in the model fitting. This results in limited compensation accuracy and applicability in scenarios with multiple materials and varying operating conditions.

[0011] In summary, existing online detection technologies for the acidity of organic compounds in liquid phases have three typical shortcomings: First, they rely solely on empirical correlations based on a single pH value, resulting in low quantitative accuracy and weak media versatility; second, adjusting ionic strength by adding inorganic salts can easily contaminate the organic materials being tested and damage the original components of the system; and third, the models depend on external indirect process parameters and do not couple the two core correction variables of measured conductivity and dilution ratio, thus limiting the corrective capabilities of the compensation models.

[0012] Therefore, there is an urgent need in this field for a novel automated acidity analysis method that couples three types of directly detectable parameters—controllable volume ratio, online measured conductivity, and measured pH of the mixed solution—to construct a multi-parameter joint compensation model. This model would enable high-precision, wide-media applicability, and fully automated online quantitative inversion of the true acidity of low-conductivity, weakly polar organic stock solutions. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model. This method fundamentally solves the system error problem of pH measurement caused by dilution, solvent differences, and low conductivity environments by constructing and utilizing a compensation model among three parameters: volume ratio, mixed liquid conductivity, and mixed liquid pH value. It accurately reflects the true acidity of the organic stock solution and achieves fully automated operation and intelligent control throughout the entire process.

[0014] To achieve the above objectives, the present invention adopts the following technical solution, providing a method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model. This method is used for the online quantitative detection of non-buffered, weakly polar organic stock solutions containing trace amounts of organic acids with a conductivity less than 100 μS / cm. The method includes: acquiring the organic stock solution and deionized water separately and performing filtration and pressure stabilization treatments on each; quantitatively mixing the treated organic stock solution and deionized water according to an adjustable preset volume ratio to obtain a mixed test solution; simultaneously collecting the pH and conductivity values ​​of the mixed test solution, and simultaneously reading the volume ratio corresponding to the current mixing ratio. These three sets of independent input variables are imported into a pre-calibrated, offline-conductivity-pH compensation model, which outputs the true acidity of the organic stock solution. The volume ratio, as an independent input variable, participates in the volume ratio-conductivity-pH compensation model to characterize the impact of dilution conditions on the system's ion activity and dielectric environment. This method relies solely on on-site measured volume ratio, pH, and conductivity values ​​to invert the acidity of the organic stock solution, without requiring pre-entry of solvent type or inherent process parameters. During online operation, the method also simultaneously executes automated control procedures: periodically calibrating the sensor using a standard pH buffer and updating the volume ratio-conductivity-pH compensation model coefficients; outputting a warning signal if the conductivity value falls below a preset threshold or if the pH value fluctuates significantly; and automatically adjusting the volume ratio when the model's confidence level does not meet the preset strategy.

[0015] Optionally, the organic stock solution to be tested and the deionized water are filtered and pressure-stabilized through independent organic stock solution pipelines and deionized water pipelines, respectively. Both the organic stock solution pipeline and the deionized water pipeline are equipped with filters and pressure stabilizing devices arranged in series. The filters adopt a membrane filtration structure to intercept solid particulate impurities in the medium. The pressure stabilizing device stabilizes the corresponding medium to a constant pressure range of 0.2 to 0.4 MPa, stabilizing the output pressure and instantaneous flow rate of the medium.

[0016] Optionally, the quantitative mixing operation according to an adjustable preset volume ratio is achieved by a proportional volume pump. The proportional volume pump has two independent media inlets, which are respectively connected to the organic stock solution pipeline and the deionized water pipeline. It can synchronously and continuously deliver the two media to the mixer according to the preset volume ratio. The volume ratio is the ratio of the volume of deionized water to the volume of organic stock solution, and the volume ratio can be adjusted from 1:1 to 10:1 to ensure that the conductivity of the mixed test solution is within the stable response range of the pH electrode.

[0017] Optionally, it also includes setting an integrated detection chamber as a detection unit, with a pH sensor and a conductivity sensor integrated inside the detection unit to simultaneously collect the pH and conductivity values ​​of the mixed test liquid; the detection unit is also equipped with a temperature control module to maintain the detection temperature of the mixed test liquid at a preset constant temperature and suppress the detection deviation caused by temperature fluctuations to the pH and conductivity values.

[0018] Optionally, the volume ratio-conductivity-pH compensation model is constructed through offline calibration. The offline calibration process is as follows: select the target type of organic stock solution, prepare multiple groups of diluted samples with different volume ratios to carry out dilution ratio experiments, and use titration to measure the true acidity of each group of organic stock solutions as the reference true value. Simultaneously collect the corresponding volume ratio, pH detection value, and conductivity detection value of each group to construct a training dataset. Fit the training dataset through at least one algorithm among multiple regression fitting, ion activity mechanism modeling, and machine learning training to obtain the volume ratio-conductivity-pH compensation model. The volume ratio-conductivity-pH compensation model establishes a nonlinear mapping relationship between volume ratio, pH detection value, conductivity detection value and the true acidity of the organic stock solution, compensates for the low conductivity of the organic stock solution, the change in ion activity coefficient caused by dilution, and the pH electrode measurement system error caused by the difference in non-aqueous dielectric environment, and inverts the true acidity of the organic stock solution that cannot be directly detected and obtained online based on the real-time collected volume ratio, pH detection value, and conductivity detection value.

[0019] Optionally, the process for determining the confidence level of the model calculation is as follows: the real-time collected volume ratio, pH detection value, and conductivity detection value are mapped to the multi-dimensional parameter space constructed by the model, and it is verified whether the volume ratio, pH detection value, and conductivity detection value fall within the parameter coverage range of the offline calibration data point set, or within the preset neighborhood corresponding to the parameter coverage range; when the deviation of the volume ratio, pH detection value, and conductivity detection value from the parameter coverage range exceeds the preset tolerance threshold, it is determined that the confidence level of the model calculation has not reached the preset qualified threshold, and the volume ratio adaptive adjustment strategy is automatically activated to gradually increase the proportion of deionized water to improve the conductivity of the mixed test liquid until any termination condition is met: the confidence level of the model calculation meets the standard, the conductivity detection value is greater than 50 μS / cm, and the fluctuation range of the pH detection value does not exceed ±0.1.

[0020] Optionally, a standard pH buffer solution is used to perform periodic calibration on the pH sensor and conductivity sensor. When the running time reaches a preset time period or the cumulative number of detections reaches a preset threshold, the control unit automatically switches the medium flow path of the detection unit to the standard pH buffer solution delivery pipeline. The standard pH buffer solution flows through the pH sensor and conductivity sensor in sequence. The control unit performs zero-point calibration and slope calibration of the pH sensor based on the collected calibration data. Based on the detection deviation before and after calibration, the offset coefficient and slope parameter in the volume ratio-conductivity-pH compensation model are iteratively optimized and updated.

[0021] Optionally, the automated control process during the online operation phase also includes: real-time acquisition of the conductivity detection value of the mixed test liquid, and statistical analysis of the change trend of the conductivity detection value within a preset time window; when the change trend of the conductivity of the mixed test liquid is continuously less than the preset lower limit threshold of conductivity, an output control command is used to increase the volume ratio of deionized water in the volume ratio until the conductivity detection value of the mixed test liquid falls into the preset qualified value range.

[0022] Optionally, the mixed test solution after acidity testing is diverted and disposed of through a pipeline switching device. When the mixed test solution meets the process reflux conditions, the pipeline switching device directly transports the mixed test solution to the organic raw material production process pipeline for recycling. When the mixed test solution does not meet the process reflux conditions, the pipeline switching device transports the mixed test solution to the organic matter recovery unit for phase separation. The organic phase obtained after phase separation is returned to the original process system, and the aqueous phase obtained after phase separation is purified and then discharged or recycled.

[0023] Optionally, the organic stock solution is a weakly polar organic solvent in a non-buffered system, selected from at least one of alcohols, ketones, esters or alkanes; the organic stock solution does not contain electrolyte components or inorganic salt components that would cause the conductivity of the diluted mixed test solution to exceed 100 μS / cm.

[0024] The organic liquid acidity detection method based on the volume ratio-conductivity-pH compensation model provided by this invention has the following significant beneficial effects.

[0025] 1. Significantly Improved Detection Accuracy, Achieving Precise Quantification of the True Acidity of Organic Stock Solutions: Existing methods for directly measuring the pH value of mixed solutions after proportional dilution are affected by various factors such as dilution, low ionic strength environment, and differences in solvent dielectric properties. These results exhibit a complex nonlinear relationship with the true acidity of the organic stock solution, typically providing only qualitative judgments and failing to provide accurate quantification, with relative measurement errors generally exceeding 15%. This invention introduces volume ratio and mixed solution conductivity as correction parameters to establish a volume ratio-conductivity-pH compensation model. This model can simultaneously compensate for ion activity distortion caused by dilution, pH electrode response drift under low conductivity conditions, and systematic errors caused by differences in the dielectric environment of different organic solvents. Verification through specific implementation methods shows that the relative error between the true acidity of the organic stock solution calculated by this model and the standard value obtained by laboratory offline titration is less than 2%, meeting the needs of high-precision quantitative monitoring of process acidity in fields such as fine chemical and pharmaceutical intermediate synthesis. Meanwhile, by combining measures such as constant temperature detection, adaptive volume ratio control, and periodic iterative correction of model coefficients, the attenuation of measurement accuracy during long-term continuous operation of the system is effectively controlled.

[0026] 2. Strong media versatility, adaptable to various weakly polar organic systems: Traditional online acidity analysis equipment is typically designed and calibrated only for single, fixed organic solvents. When the type of material to be tested changes, it is often necessary to replace the sensor or re-establish and adjust the fixed dilution ratio, leading to extended production line downtime. This invention adopts a universal input variable design, eliminating the need to pre-enter specific solvent types or complex process parameters during online operation. For novel organic materials, only a small number of offline dilution ratio calibration experiments with gradients are required to build a dedicated compensation model before application. This method is compatible with various single or mixed organic materials such as alcohols, ketones, esters, and alkanes, significantly enhancing its applicability in flexible continuous chemical production lines with alternating production of multiple products, effectively reducing production line debugging and downtime caused by product switching.

[0027] 3. Achieve Full-Process Automated Operation: This method achieves fully automated closed-loop control from media filtration and pressure stabilization, proportional dilution and mixing, simultaneous detection of pH and conductivity, automatic acidity calculation based on models, periodic sensor calibration, operational status early warning, to the diversion and recycling of the detected media. The entire process eliminates the need for manual on-site sampling, offline titration, manual equipment calibration, or ratio adjustment. Detection data can be uploaded to the distributed control system in real time, enabling automatic interlocking with process feed or neutralizer addition control links, replacing the traditional process control mode that relies on manual testing and adjustment. Simultaneously, this automated process avoids operators directly contacting high-temperature, flammable, and explosive organic materials for sampling, fundamentally reducing the safety risks of volatilization poisoning, combustion, and explosion.

[0028] 4. Features an intelligent anti-interference control mechanism and high operational stability: By monitoring the conductivity of the mixed solution in real time to characterize the ionic state of the solution, and combining multiple control logics such as model confidence assessment, adaptive volume ratio adjustment (e.g., actively increasing the aqueous phase ratio when conductivity remains consistently low), and pH fluctuation warning, the system can automatically offset detection interference introduced by factors such as batch differences in materials, ambient temperature fluctuations, or minor pipeline blockages. When real-time detection data deviates from the reliable parameter range calibrated offline by the model, the system can automatically adjust the volume ratio to bring the measurement system back to a stable state. Compared to detection equipment using a fixed volume ratio, this method exhibits stronger anti-interference capabilities and operational stability when facing complex and fluctuating operating conditions, making it suitable for continuous synthesis or distillation production units with large fluctuations in operating conditions.

[0029] 5. Effectively extends sensor lifespan and reduces maintenance costs: In existing technologies, pH electrodes typically come into direct contact with high-concentration organic solutions. Organic colloids or trace amounts of organic acids in these solutions easily adhere to or corrode the electrode's sensitive membrane, resulting in a short average electrode lifespan of only 1 to 3 months, increasing replacement and maintenance costs. This invention employs a method of diluting the organic solution with deionized water in a specific ratio to form a mixture before detection. This ensures the sensor electrode primarily contacts the water-organic mixture, significantly reducing the direct impact of high-concentration organic matter on the electrode. Combined with regular automatic cleaning and calibration using a standard pH buffer solution, the frequency of manual disassembly and maintenance is reduced. As a result, the sensor electrode's lifespan is significantly extended to over 12 months, thereby substantially reducing sensor replacement costs and related maintenance expenses.

[0030] 6. Achieving closed-loop management and recycling of the testing media, resulting in significant environmental and economic benefits: The system incorporates a diversion and disposal mechanism for the mixed liquid after testing. Mixed liquids meeting process reuse requirements can be directly recycled back into the production process; those not meeting direct reuse requirements are transported to a dedicated organic matter recovery unit for phase separation. The separated organic phase can be returned to the original process system, while the aqueous phase, after purification, can be recycled for dilution or discharged in compliance with standards. Compared to laboratory offline titration methods, which consume large amounts of organic raw material samples and generate acidic or alkaline waste liquid for each test, this method achieves near-zero material loss and significantly reduces the generation and disposal of hazardous waste, lowering raw material costs and environmental disposal expenses, thus meeting the requirements of clean production and circular economy development in the chemical industry. Attached Figure Description

[0031] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0032] Figure 1 This is an overall flowchart of the organic liquid acidity detection method based on the volume ratio-conductivity-pH compensation model of the present invention.

[0033] Figure 2 This is a block diagram illustrating the offline calibration and online application principle of the volume ratio-conductivity-pH compensation model in this invention.

[0034] Figure 3 This is a flowchart of the automated intelligent control logic in this invention. Detailed Implementation

[0035] The embodiments of this application will now be described in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, the following embodiments and features can be combined with each other unless otherwise specified. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0036] To address the problems of dilution nonlinearity interference, low conductivity pH electrode drift, poor compatibility with multiple organic solvents, lack of automatic correction and control, and insufficient measurement accuracy in existing fixed dilution direct pH detection methods, this invention provides an organic liquid acidity detection method based on a volume ratio-conductivity-pH compensation model, achieving the following objectives: (1) Constructing a coupled compensation model of three parameters (volume ratio, pH of the mixed liquid, and conductivity of the mixed liquid) (i.e., volume ratio-conductivity-pH compensation model) to eliminate pH measurement system deviations caused by dilution effects, low ionic strength, and non-aqueous dielectric environments, accurately retrieving the true acidity of the organic stock solution from the measured data of the mixed liquid, and realizing quantitative online detection. (2) Offline model calibration only requires true value titration data of the corresponding type of organic stock solution, and online operation does not require pre-entry of solvent type and inherent process parameters, and is compatible with multiple weakly polar organic materials such as alcohols, ketones, esters, and alkanes, improving the versatility of the equipment media. (3) Fully automated intelligent control process: periodic automatic sensor calibration and model coefficient iterative update, low conductivity / large pH fluctuation fault warning, adaptive adjustment of dilution water ratio when model confidence is insufficient, no manual intervention required throughout the process. (4) Optimize the whole process structure of pre-treatment, synchronous detection and post-treatment recycling, reduce electrode organic pollution, extend sensor life, and the mixed medium after detection can be recycled or the organic matter can be separated and recycled, reducing material loss and hazardous waste production. (5) The overall process is compatible with industrial continuous closed production lines and can be directly connected to DCS automatic control system to realize real-time acidity data upload and process interlock automatic control, solving the problems of offline titration lag and safety risks of manual sampling.

[0037] Please see the appendix Figure 1 The entire detection method of this invention consists of five core continuous processes: media pretreatment process, quantitative mixing process, multi-parameter synchronous online detection process, volume ratio-conductivity-pH compensation model compensation calculation and intelligent automatic control process, and detection media post-processing diversion and recovery process; it is equipped with an offline model calibration preprocess, and during the online operation phase, three major automated control logics are executed simultaneously: automatic sensor calibration, anomaly warning, and adaptive ratio adjustment. The overall technical solution is described in detail step by step as follows.

[0038] S1, Media pretreatment.

[0039] Two media were collected: the organic stock solution to be tested and deionized water. Each media underwent independent filtration and pressure stabilization pretreatment. Specifically, two independent closed-loop delivery pipeline systems were set up. One pipeline was used to transport the organic stock solution, and the other was used to transport high-purity deionized water with a conductivity controlled below 0.1 μS / cm. The two media underwent independent filtration and pressure stabilization pretreatment along their respective pipelines to eliminate the adverse effects of solid impurities and fluid pressure fluctuations on dilution accuracy and sensor lifespan.

[0040] The pipeline structure for this step is as follows: both the organic raw material delivery pipeline and the deionized water delivery pipeline are equipped with filters and pressure stabilizing devices in series; the filters are equipped with multi-layer organic solvent resistant filter membrane components, which can intercept trace polymers, catalyst solid particles, pipeline corrosion impurities in organic materials, and prevent downstream proportional volume pumps, mixers, detection chambers, and sensing electrodes from clogging, mechanical wear, and organic adhesion contamination; the filter membrane pore size can be selected in the range of 0.22μm to 5μm according to the impurity content of organic materials, adapting to various production conditions.

[0041] The pressure stabilization control mechanism in this step is as follows: two pressure stabilizing devices constantly regulate the output pressure of the medium to the range of 0.2MPa to 0.4MPa, with the preferred pressure stabilization setting value being 0.3MPa; the pressure stabilizing device integrates a real-time pressure acquisition and feedback module, and when the pipeline fluid pressure deviates from the preset pressure range, the device automatically adjusts the opening of the matching valve to stabilize the instantaneous output flow of the medium, ensuring that the subsequent volume ratio is accurately controllable in the long term, and avoiding the system error in model calculation caused by pressure fluctuations leading to ratio deviation.

[0042] After filtration and pressure stabilization pretreatment, the organic raw liquid and deionized water are respectively connected to two independent media input ports of the proportional volumetric pump to complete the media pretreatment process and transport them to the downstream process.

[0043] S2, quantitative mixing.

[0044] A dual-path independent drive proportional volumetric pump is used to achieve continuous, synchronous, and quantitative delivery of organic stock solution and deionized water, and to prepare a uniformly mixed test solution according to an adjustable preset volume ratio.

[0045] This step employs a proportional volumetric pump to achieve quantitative mixing and delivery of two media streams. This pump has two independent media input channels with non-interfering flow paths. These two input channels are connected to the organic raw material delivery pipeline and the deionized water delivery pipeline, respectively, after the pretreatment process. The pump body is equipped with two independent metering drive mechanisms, capable of precisely controlling the instantaneous volumetric flow rate of the two media streams and synchronously and continuously delivering them to the downstream mixer cavity. The mixer cavity is equipped with multi-layered turbulence-inducing components, which enhances the mass transfer and mixing effect between the organic and aqueous phases, promoting rapid homogeneous fusion of the two phases, preventing local concentration stratification within the mixture, and avoiding distortion in multi-parameter acquisition in the detection chamber caused by uneven media composition.

[0046] This invention defines the volume ratio as the ratio of deionized water volume to organic stock solution volume, with an adjustable control range of 1:1 to 10:1. The lower limit of 1:1 aims to simplify the dilution process and reduce water consumption. The upper limit of 10:1 is suitable for extreme conditions where the organic stock solution has extremely low ion content and the conductivity of the diluted test solution approaches the effective response limit of the pH electrode. By increasing the proportion of deionized water in the dilution system through the control system, the overall ionic strength of the mixed test solution can be improved, ensuring the conductivity of the mixture remains stably within the reliable response range of the pH electrode, thus suppressing electrode potential measurement drift from the perspective of equipment hardware structure.

[0047] In this step, compared with existing online detection equipment that uses a fixed dilution ratio, the present invention can dynamically adjust the volume ratio in real time based on the type of organic material, the impurity content of the raw material batch, and the confidence index calculated online by the model, providing a hardware execution basis for the system's post-adaptive ratio control logic.

[0048] S3. Multi-parameter synchronous online detection.

[0049] After thorough homogenization and mixing, the test liquid is continuously fed into the integrated detection chamber (as a detection unit) to simultaneously acquire two physical property parameters of the mixture: pH and conductivity. The detection unit is equipped with a built-in temperature control module to eliminate measurement deviations caused by fluid temperature fluctuations.

[0050] The integrated detection chamber adopts an integrated assembly structure: pH sensor and conductivity sensor are arranged in the same cavity inside the detection chamber. The two types of sensors are simultaneously immersed in the same mixed test liquid flow channel, which can realize the synchronous acquisition of two sets of parameters under the same medium conditions at the same time. This avoids the problem of multi-parameter mismatch caused by misalignment of acquisition time sequence and stratification of medium components, and ensures that the three sets of model input variables of volume ratio, pH detection value and conductivity detection value have spatiotemporal consistency, effectively improving the accuracy of the calculation results of volume ratio-conductivity-pH compensation model.

[0051] The constant temperature anti-interference correction mechanism of the chamber is as follows: The detection chamber is equipped with a closed-loop temperature control module, which can stably maintain the mixed test liquid flowing through the chamber at a preset constant detection temperature. The standard offline calibration reference temperature is selected as 25℃, which can be flexibly adjusted according to the actual production process conditions on site. Temperature conditions will simultaneously change the organic acid dissociation equilibrium state, solution ion migration rate, pH electrode liquid junction potential and solution conductivity values. The constant temperature condition can unify the temperature reference of the offline calibration stage and the online detection stage, eliminate multi-dimensional temperature coupling interference, and reduce the correction load of the compensation model.

[0052] Real-time data transmission process: The pH and conductivity values ​​collected by the pH and conductivity sensors are synchronously transmitted to the control unit in real time along with the currently set volume ratio of the proportional volume pump. These values ​​serve as three independent input variables for the volume ratio-conductivity-pH compensation model.

[0053] S4, Volume ratio-conductivity-pH compensation model compensation calculation and intelligent automatic control.

[0054] The core distinguishing technical feature of this invention is that it simultaneously executes offline model calibration, online real-time compensation calculation, and multiple sets of automated intelligent control processes in the detection process, thereby differentiating itself from existing conventional detection methods that only directly measure the pH of the mixed solution.

[0055] 1. Offline calibration process for constructing a volume ratio-conductivity-pH compensation model: Before the online detection process is put into use, an offline calibration operation is performed on the organic raw liquid of the target product to be detected, a standardized training dataset is constructed and a compensation model is fitted. The complete calibration operation process is as follows.

[0056] (1) Select organic raw liquid to be tested that is from the same source as the material in the production line, and use the laboratory standard acid-base potentiometric titration method to determine the true acidity of the organic raw liquid. Use the true value obtained from the titration as the benchmark reference value for model fitting calculation.

[0057] (2) Adjust the proportional volume pump to configure multiple gradient volume ratios, and the gradient ratios fully cover the entire adjustable range from 1:1 to 10:1. Repeat the parallel dilution test 3 to 5 times under each dilution ratio condition.

[0058] (3) The diluted samples of each group are transported to the integrated constant temperature detection chamber, and the corresponding volume ratio, pH detection value and conductivity detection value are collected and recorded simultaneously.

[0059] (4) Summarize all the test data of the gradient ratio test and construct a standardized training dataset. The dataset uses volume ratio, pH value and conductivity value as input variables and the true acidity of organic stock solution as the output true value.

[0060] (5) Select at least one of the following algorithms to perform fitting operations on the training dataset: multiple linear regression, multiple nonlinear regression, ion activity mechanism modeling, and shallow machine learning training. Establish a nonlinear mapping relationship between the three sets of input variables and the actual acidity of the organic raw material, and obtain a specific volume ratio-conductivity-pH compensation model suitable for this type of organic material.

[0061] (6) The correction mechanism of the compensation model is as follows: synchronously coupling three types of parameters: volume ratio, system ion concentration characterized by conductivity, and acidity of the mixed solution, and synchronously compensating for three types of systematic measurement errors: a) deviation caused by nonlinear change in hydrogen ion activity coefficient due to water dilution; b) deviation caused by liquid junction potential shift and response lag of pH electrode under low conductivity organic medium conditions; c) pH measurement benchmark shift deviation caused by differences in dielectric constant of different organic solvents. When using the volume ratio-conductivity-pH compensation model obtained by this calibration, the true acidity of the organic raw solution that cannot be directly detected online can be inverted by relying only on the three sets of parameters obtained by real-time on-site measurement; during the online detection process, there is no need to pre-enter material characteristic parameters such as solvent type and inherent impurities in the process; after changing the production material, only one round of offline calibration needs to be completed again to continue online acidity detection.

[0062] 2. Online Real-Time Compensation Calculation Process: When continuously performing online acidity detection, the detection unit retrieves a pre-stored volume ratio-conductivity-pH compensation model adapted to the current material. The three sets of independently measured variables—volume ratio, pH value, and conductivity value—collected synchronously in real time are substituted into the volume ratio-conductivity-pH compensation model for calculation. This dynamically eliminates all system measurement deviations caused by dilution effects, low-conductivity media, and solvent property differences, directly outputting the true acidity of the organic raw material. The calculated true acidity of the organic raw material is transmitted in real time to the plant's DCS control system for real-time monitoring of the production process and automatic interlocking control of the acidity adjustment process.

[0063] 3. The online testing process simultaneously executes four automated intelligent control processes, specifically including the following steps.

[0064] (1) Periodic automatic calibration of sensors and iterative update of model coefficients: During long-term continuous testing, the electrodes of the pH sensor and the conductivity sensor are prone to aging, scaling, and zero-point potential drift. The performance degradation of these two types of sensors will lead to mismatch of the fixed coefficients of the volume ratio-conductivity-pH compensation model, resulting in calculation errors. This method sets up a fully automatic periodic calibration process, which will automatically start the calibration process when any of the following trigger conditions are met: the cumulative continuous running time of the equipment reaches the preset time period (configurable to 24h, 72h, etc.); the cumulative total number of tests of the equipment reaches the preset counting threshold (configurable to 500 times, 1000 times, etc.).

[0065] The calibration process is as follows: The control unit automatically switches the media flow pipeline, cuts off the feed path of organic raw solution and deionized water, and connects the standard pH buffer delivery pipeline to the detection chamber; the standard pH buffer continuously flows through the pH sensor and conductivity sensor to complete the sensor calibration; the pH electrode zero point correction and slope correction are completed based on the pH buffer calibration data; the deviation of the detection values ​​under the same working conditions before and after calibration is compared, the internal offset coefficient and slope parameters of the volume ratio-conductivity-pH compensation model are iteratively optimized, and the local model storage database is automatically updated to ensure long-term stable detection accuracy without the need for manual disassembly of the sensor electrodes for offline calibration.

[0066] (2) Automatic early warning process for low conductivity and large pH fluctuation of mixed solution: The control unit collects and monitors the pH and conductivity values ​​of the mixed test solution in real time. If the conductivity value is continuously lower than the preset lower limit threshold, it indicates that the ionic strength of the system is insufficient and the stability of the sensor electrode measurement is lost. Simultaneously, the on-site audible and visual early warning signal and the remote DCS system pop-up early warning signal are triggered. If the fluctuation range of the pH value within a unit statistical time window exceeds the preset fluctuation threshold (typical threshold is ±0.2), it is determined that there is a pipeline blockage, proportional volume pump ratio failure, or sensor electrode surface contamination fault. Simultaneously, a fault early warning signal is output to prompt the operation and maintenance personnel to conduct fault investigation on the delivery pipeline, metering pump, and sensor.

[0067] (3) Model calculation confidence determination and volume ratio adaptive adjustment process: By determining the model calculation confidence, it is determined whether the three sets of parameters, namely volume ratio, pH detection value and conductivity detection value, collected in real time, fall within the parameter coverage range of the offline calibration dataset, so as to avoid large calculation errors caused by parameter extrapolation. The complete determination and adaptive adjustment operation process is as follows.

[0068] The real-time collected volume ratio, pH value, and conductivity value are mapped to the three-dimensional parameter space formed by offline calibration. It is verified whether the three sets of parameters are within the complete coverage range of the calibration data points, or within the preset tolerance neighborhood corresponding to the coverage range. If the three sets of parameters deviate from the calibration parameter coverage range and exceed the preset tolerance threshold, the model calculation confidence level is determined to be below the acceptable standard, and the volume ratio adaptive adjustment process is initiated. The control unit progressively increases the volume ratio of deionized water in the dilution system to continuously improve the overall ionic strength of the mixed test solution. The dilution ratio adjustment operation is stopped when any of the following control termination conditions are met: the model calculation confidence level returns to the acceptable range, the conductivity value is greater than 50 μS / cm, and the fluctuation range of the pH value obtained from three consecutive tests does not exceed ±0.1. By automatically increasing the dilution water ratio to improve the ion concentration of the system, the detection conditions are adjusted to the reliable parameter range of the model calibration, ensuring that the acidity calculation results output by the model are true and effective.

[0069] (4) Automatic control process for adjusting the dilution water ratio under the condition of continuous low conductivity: This method is equipped with an independent conductivity change trend monitoring step. It continuously counts the continuous change trend of the conductivity of the mixture within the preset time window. If the conductivity detection value is continuously low and long-term below the preset qualified lower limit threshold, there is no need to execute the model confidence judgment process. Instead, it directly outputs the ratio adjustment control command to increase the deionized water volume ratio, actively improves the ion strength of the mixed test liquid, and reduces the pH measurement drift deviation caused by low conductivity conditions from the source.

[0070] S5. After detection, the mixed media is diverted and then processed for recycling.

[0071] After parameter acquisition and model calculation, the mixed test liquid is diverted to a dual-path system via a pipeline switching valve to achieve resource recycling and reduce raw material loss and hazardous waste generation. The specific diversion and disposal methods are divided into two categories: process reflux and recovery separation. (1) Process reflux: When the water content and impurity content of the mixed test liquid meet the requirements of the production process reflux index, the pipeline switching device directly transports the mixed medium to the main process pipeline of the organic raw liquid production to complete the recycling of organic materials without raw material loss. (2) Recovery separation: If the mixed test liquid does not meet the process reflux conditions, it is transported to the organic recovery unit through the pipeline switching valve. At least one phase separation process, such as static stratification and extraction distillation, is used to complete the separation of the organic phase and the aqueous phase. The organic phase obtained after phase separation is transported back to the production line for recycling. The aqueous phase obtained after separation is purified by activated carbon adsorption and ion exchange resin in sequence. It is discharged or reused according to the water quality index and can be used as dilution deionized water to participate in the detection process, which significantly reduces the cost of hazardous waste disposal.

[0072] The organic liquid acidity detection method provided by this invention is applicable to weakly polar organic stock solutions without buffering. The organic stock solution can be a single solvent or a mixture of solvents such as alcohols, ketones, esters, and alkanes. The organic stock solution does not contain high concentrations of inorganic salts and strong electrolyte components. The conductivity of the mixed test solution prepared after dilution with deionized water is stably lower than 100 μS / cm. The organic stock solution contains only trace amounts of organic acids as the target substances for acidity detection. The system does not contain strong buffering components that can offset the changes in ion activity caused by dilution. This method is compatible with the correction mechanism of the volume ratio-conductivity-pH compensation model constructed in this invention.

[0073] In summary, the complete detection process of this invention is as follows: Two media, the organic raw solution to be tested and high-purity deionized water, are delivered separately; each media undergoes filtration and pressure stabilization pretreatment along independent pipelines; the pretreated media are quantitatively delivered to the mixer according to an adjustable volume ratio using a proportional volumetric pump and fully homogenized to obtain a mixed test solution; the mixed test solution is introduced into an integrated constant-temperature detection chamber, and pH and conductivity values ​​are simultaneously collected; the control unit reads the real-time volume ratio, pH value, and conductivity value, and substitutes them into the pre-calibrated offline parameters. The volume ratio-conductivity-pH compensation model is used to calculate and output the true acidity of the organic raw solution. The online detection process simultaneously and in parallel executes automatic sensor calibration, volume ratio adaptive adjustment based on model confidence, and early warning control for low conductivity anomalies and large pH fluctuations. After the detection calculation is completed, the mixed test solution is diverted and disposed of through pipeline switching valves. The medium that meets the reflux index is directly transported back to the production process for recycling, while the medium that does not meet the reflux conditions is transported to the organic matter recovery unit for phase separation and resource recovery. The entire process is closed, continuous, and automated.

[0074] The present invention will be described in detail below with reference to the embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of protection. The technical features in the embodiments can be combined with each other.

[0075] The test object in this embodiment is the ethyl acetate organic stock solution from the esterification production line. The stock solution contains trace amounts of acetic acid, no inorganic salts, and no buffer components. The conductivity of the diluted mixture is <100μS / cm, which is within the scope of application of this invention.

[0076] Basic operating conditions settings: conductivity of diluted deionized water 0.08 μS / cm; target medium pressure 0.3 MPa; initial volume ratio R = 3:1; constant temperature of detection chamber 25℃; offline calibration using multivariate nonlinear regression; conductivity warning lower limit 1 μS / cm; pH fault warning threshold ±0.2; pH stabilization threshold for termination of ratio control ±0.1; automatic calibration cycle 72h.

[0077] This embodiment specifically performs the following steps.

[0078] 1. Media Pretreatment: Ethyl acetate organic raw material is continuously drawn from the side stream of the production distillation tower and sent to an independent organic pipeline. It passes through a 5μm organic compatible membrane filter to remove polymer and catalyst solid impurities. The downstream pressure stabilizing device keeps the pipeline medium pressure stable at 0.3MPa, and the instantaneous flow rate is constant. The deionized water from the dilution tank enters an independent water pipeline and is filtered through a 0.22μm precision membrane to remove trace ionic impurities in the water. The pressure stabilizing device simultaneously stabilizes the pressure to 0.3MPa. The two pretreated media are respectively connected to the two input channels of the dual proportional volumetric pumps.

[0079] 2. Quantitative mixing: Two proportional volumetric pumps are set to deliver the flow rate, and the volume ratio between deionized water and organic stock solution is controlled at 3:1. The two media are synchronously and continuously delivered to the mixer with built-in multi-layer turbulence blades. The media are turbulently stirred inside the mixer for 3 seconds to complete complete homogenization and fusion, without local organic acid concentration stratification, and stably output uniformly mixed test solution to the back-end integrated detection chamber.

[0080] 3. Multi-parameter synchronous online detection: The mixed test liquid continuously flows into the integrated sealed detection chamber, and the chamber temperature control module continuously exchanges heat to keep the medium temperature stable at 25℃; a composite pH sensor and a four-electrode conductivity sensor are installed simultaneously inside the chamber, and two sets of parameters are collected at the same time and transmitted to the control unit in real time. The stable parameters measured in this online test are: pH value of 3.2, conductivity value of 2.1μS / cm, and current volume ratio of 3.

[0081] 4. Compensation calculation and intelligent automatic control of the volume ratio-conductivity-pH compensation model, specifically including the following steps.

[0082] (1) Preliminary offline calibration process (completed before equipment commissioning): 1) Collect ethyl acetate stock solution from the same batch of production line and measure the true acidity gradient sample of the stock solution by laboratory potentiometric titration; 2) Set six dilution ratios with volume ratios of 1:1, 2:1, 3:1, 5:1, 8:1, and 10:1, and repeat each ratio 4 times in parallel; 3) Record the volume ratio, pH value, and conductivity value of each ratio simultaneously, and summarize all experimental data to construct a training dataset; 4) Use a multivariate nonlinear regression algorithm to fit the dataset and obtain the volume ratio-conductivity-pH compensation model formula suitable for the ethyl acetate system: True acidity of organic stock solution = 0.32 × pH The formula is: Detected value + 0.21 × Conductivity Detected value - 0.08 × Volume ratio + 1.62, where 0.32 is the correlation weight of the mixed solution pH, used to scale up pH value distortion caused by dilution; 0.21 is the conductivity correction weight, to compensate for pH electrode drift error under low ionic strength; -0.08 is the volume ratio correction coefficient, to offset acidity shift caused by different dilution factors; and the constant term 1.62 is the comprehensive baseline shift compensation amount, uniformly correcting residual systematic errors caused by organic solvent dielectric effect, electrode baseline, and non-ideal dissociation of organic acids. All four sets of coefficients are obtained by multivariate regression fitting of the ethyl acetate system gradient dilution calibration dataset and are only suitable for this ester organic detection system. 5) Store the model coefficients in the local database of the control unit to complete offline calibration (see Appendix). Figure 2 ).

[0083] (2) Online real-time model calculation: Substituting the measured volume ratio = 3, pH value = 3.2, and conductivity value = 2.1 μS / cm into the above volume ratio-conductivity-pH compensation model, the specific calculation is: 0.32 × 3.2 + 0.21 × 2.1 - 0.08 × 3 + 1.62 = 1.024 + 0.441 - 0.24 + 1.62 ≈ 2.8

[0084] (3) True value verification and error analysis: The batch of ethyl acetate organic stock solution samples were collected simultaneously, and the true acidity of the stock solution was determined by laboratory standard acid-base potentiometric titration, with a reference value of 2.75. The calculated acidity value obtained by the volume ratio-conductivity-pH compensation model of this invention was 2.8, and the relative error was calculated as (2.8-2.75) / 2.75×100%≈1.82%. The relative error of the detection was controlled within 2%, which can meet the accuracy requirements of online quantitative detection in industrial settings. If the existing conventional fixed dilution direct pH detection scheme is used, and the pH detection value = 3.2 is directly used as the basis for judging the acidity of the organic stock solution, the relative deviation of this value from the titration reference value of 2.75 reaches 16.36%, and the quantitative error is too large, which does not have the value of process closed-loop control. The comparison results can fully prove that the volume ratio-conductivity-pH compensation model of this invention has excellent measurement deviation correction capability.

[0085] Please see the appendix Figure 3 The implementation effects of the online automated collaborative control process are as follows.

[0086] (1) Implementation process of periodic automatic calibration of sensor: When the equipment has accumulated a continuous running time of 72h preset period, the control and calculation unit automatically completes the switching of the medium flow pipeline, cuts off the feed path of organic raw liquid and deionized water, and introduces two sets of standard buffer solutions of pH=4.0 and pH=6.86 into the detection chamber in sequence and continuously flushes the pH sensor and conductivity sensor; the system completes the zero point correction and slope correction of pH electrode based on the buffer calibration data, compares the deviation of the detection values ​​before and after calibration under the same working conditions, iteratively updates the built-in offset coefficient of the compensation model, and eliminates the potential drift error caused by the long-term operation and aging of the electrode.

[0087] (2) Demonstration of adaptive volume ratio control driven by model confidence: When the organic acid content of the ethyl acetate stock solution in the production unit drops significantly, the measured conductivity value drops to 0.8 μS / cm. After mapping this set of parameters to the offline calibration three-dimensional parameter space, it is determined that the measured parameters exceed the coverage range of the calibration dataset, and the confidence of the model calculation is not up to standard. The deionized water ratio in the dilution system is gradually increased, and the volume ratio is adjusted to 6:1. The conductivity of the mixed test solution is simultaneously increased to 38 μS / cm. The volume ratio is further adjusted to 8:1. At this time, the conductivity of the mixed solution reaches 52 μS / cm, which meets the control termination condition that the conductivity value is greater than 50 μS / cm, and the ratio adjustment process stops. Multiple sets of parameters under steady state are re-acquired and substituted into the volume ratio-conductivity-pH compensation model for calculation. The test condition returns to the model's reliable parameter range.

[0088] (3) Demonstration of abnormal operating conditions: When a minor blockage occurs in the pipeline filter, the instantaneous flow rate of deionized water decreases, and the volume ratio becomes unbalanced; the fluctuation range of the pH detection value within a 5-minute statistical window reaches ±0.25, exceeding the preset fluctuation warning threshold. The on-site audible and visual warning signal is output simultaneously, along with the remote pop-up fault prompt of the plant's DCS control system. After the maintenance personnel replace the blocked filter membrane, the pipeline flow rate returns to stability, and the warning signal is automatically deactivated.

[0089] 5. Post-detection media diversion and recovery process: In this embodiment, the mixed dilution liquid of the esterification production line has a low water content, which meets the process reflux standard. The pipeline switching valve automatically sends the mixed test liquid directly back to the feed pipeline of the distillation tower. The ethyl acetate organic phase is recycled and reused without material loss. If impurities are mixed in during the later water washing process of the production line and the water content of the mixed liquid exceeds the standard, the switching valve automatically switches to the organic matter recovery unit. After static stratification and separation of the organic ester phase and the aqueous phase, the ethyl acetate organic phase is sent back to the distillation system, and the aqueous phase is purified by activated carbon adsorption and ion exchange resin and then recycled as diluted deionized water.

[0090] Multi-material switching process: This invention is adaptable to organic stock solutions of ethanol (alcohols), acetone (ketones), and n-hexane (alkanes). Switching materials only requires re-performing gradient dilution offline calibration to generate a dedicated volume ratio-conductivity-pH compensation model, without replacing equipment hardware or modifying pipeline structure. Taking the ethanol-trace acetic acid system as an example, multiple sets of volume ratio, pH detection values, conductivity detection values, and titration true values ​​are collected offline. The volume ratio-conductivity-pH compensation model of the new ethanol system is fitted and stored in the control unit for direct online detection. The equipment has significant advantages in terms of media versatility.

[0091] This embodiment employs the detection method of the present invention, which, compared to traditional fixed-dilution direct pH online measurement equipment, reduces the relative measurement error from over 16% to within 2%; it operates continuously and automatically 24 / 7 without the need for manual sampling, calibration, or calculation; the electrode lifespan of the pH sensor is extended from 3 months to 12 months; all organic materials are recovered and reused after detection, with no large-scale production of hazardous waste or waste liquid; material switching requires only a single offline calibration, reducing production line downtime for debugging by 90%, and completely solving all the technical pain points of existing online detection of acidity in industrial organic liquid phases.

[0092] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for detecting the acidity of organic liquids based on a volume ratio-conductivity-pH compensation model, used for the online quantitative detection of non-buffered, weakly polar organic stock solutions containing trace amounts of organic acids with a mixed test liquid conductivity less than 100 μS / cm, characterized in that... include: The organic stock solution to be tested and deionized water were obtained separately and then filtered and pressure stabilized. The treated organic stock solution and deionized water are quantitatively mixed according to an adjustable preset volume ratio to prepare a mixed test solution; The pH and conductivity values ​​of the mixed test solution are collected simultaneously, and the volume ratio corresponding to this preparation is read simultaneously. These are used as three independent input variables and imported into a pre-calibrated volume ratio-conductivity-pH compensation model. The model calculates and outputs the true acidity of the organic stock solution. Among them, the volume ratio is used as an independent input variable in the volume ratio-conductivity-pH compensation model to characterize the effect of dilution conditions on the ion activity and dielectric environment of the system. This method only relies on the volume ratio, pH value and conductivity value obtained by field measurement to complete the acidity inversion of organic stock solution, without the need to pre-enter solvent type and inherent process characteristic parameters. During the online operation phase, the method also simultaneously executes an automated control process: periodically calibrating the sensor using a standard pH buffer solution and updating the coefficients of the volume ratio-conductivity-pH compensation model; outputting an early warning signal if the conductivity detection value is lower than the preset threshold or the pH detection value fluctuates significantly; and automatically adjusting the volume ratio when the model calculation confidence does not meet the preset strategy.

2. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The organic raw solution and deionized water to be tested are filtered and pressure-stabilized through independent organic raw solution pipelines and deionized water pipelines, respectively. Both the organic raw solution pipeline and the deionized water pipeline are equipped with filters and pressure stabilizing devices arranged in series. The filters adopt a membrane filtration structure to intercept solid particulate impurities in the medium. The pressure stabilizing device stabilizes the corresponding medium to a constant pressure range of 0.2 to 0.4 MPa, stabilizing the output pressure and instantaneous flow rate of the medium.

3. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The quantitative mixing operation according to an adjustable preset volume ratio is achieved by a proportional volume pump. The proportional volume pump has two independent media inlets, which are connected to the organic stock solution pipeline and the deionized water pipeline, respectively. It can synchronously and continuously deliver the two media to the mixer according to the preset volume ratio. The volume ratio is the ratio of the volume of deionized water to the volume of organic stock solution, and the volume ratio can be adjusted from 1:1 to 10:1 to ensure that the conductivity of the mixed test solution is within the stable response range of the pH electrode.

4. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, It also includes setting up an integrated detection chamber as a detection unit, with a pH sensor and a conductivity sensor integrated inside the detection unit to simultaneously collect the pH and conductivity values ​​of the mixed test liquid; the detection unit is also equipped with a temperature control module to maintain the detection temperature of the mixed test liquid at a preset constant temperature, suppressing the detection deviation caused by temperature fluctuations to the pH and conductivity values.

5. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The volume ratio-conductivity-pH compensation model is constructed by offline calibration. The offline calibration process is as follows: select the target category of organic stock solution, prepare multiple groups of diluted samples with different volume ratios to carry out dilution ratio tests, use titration to measure the true acidity of each group of organic stock solution as the reference true value, and simultaneously collect the corresponding volume ratio, pH detection value, and conductivity detection value of each group to construct a training dataset. By fitting the training dataset using at least one algorithm among multiple regression fitting, ion activity mechanism modeling, and machine learning training, a volume ratio-conductivity-pH compensation model is obtained. This model establishes a nonlinear mapping relationship between volume ratio, pH detection value, conductivity detection value, and the true acidity of the organic stock solution. It compensates for the system errors in pH electrode measurement caused by the low conductivity of the organic stock solution, the change in ion activity coefficient due to dilution, and the difference in non-aqueous dielectric environment. Based on the real-time collected volume ratio, pH detection value, and conductivity detection value, the true acidity of the organic stock solution, which cannot be directly detected and obtained online, is inverted.

6. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The process for determining the confidence level of the model calculation is as follows: The real-time collected volume ratio, pH value, and conductivity value are mapped to the multi-dimensional parameter space constructed by the model. It is verified whether the volume ratio, pH value, and conductivity value fall within the parameter coverage range of the offline calibration data point set, or within the preset neighborhood corresponding to the parameter coverage range. When the deviation of the volume ratio, pH value, and conductivity value from the parameter coverage range exceeds the preset tolerance threshold, it is determined that the confidence level of the model calculation has not reached the preset qualified threshold. The adaptive adjustment strategy of volume ratio is automatically activated, and the proportion of deionized water is gradually increased to improve the conductivity of the mixed test solution until any termination condition is met: the confidence level of the model calculation meets the standard, the conductivity value is greater than 50 μS / cm, and the fluctuation range of the pH value does not exceed ±0.

1.

7. The method for detecting the acidity of organic liquid based on the volume ratio-conductivity-pH compensation model according to claim 4, characterized in that, The pH sensor and conductivity sensor are periodically calibrated using a standard pH buffer solution. When the running time reaches a preset time period or the cumulative number of detections reaches a preset threshold, the control unit automatically switches the medium flow path of the detection unit to the standard pH buffer solution delivery pipeline. The standard pH buffer solution flows through the pH sensor and conductivity sensor in sequence. Based on the collected calibration data, the control unit performs zero-point calibration and slope calibration of the pH sensor. Based on the detection deviation before and after calibration, the offset coefficient and slope parameter in the volume ratio-conductivity-pH compensation model are iteratively optimized and updated.

8. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The automated control process during the online operation phase also includes: real-time acquisition of the conductivity detection value of the mixed test liquid and statistical analysis of the change trend of the conductivity detection value within a preset time window; when the change trend of the conductivity of the mixed test liquid is continuously less than the preset lower limit threshold of conductivity, the output control command is used to increase the volume ratio of deionized water in the volume ratio until the conductivity detection value of the mixed test liquid falls into the preset qualified value range.

9. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, After acidity testing, the mixed test solution is diverted and disposed of through a pipeline switching device. When the mixed test solution meets the process reflux conditions, the pipeline switching device directly transports the mixed test solution to the organic raw material production process pipeline for recycling. When the mixed test solution does not meet the process reflux conditions, the pipeline switching device transports the mixed test solution to the organic matter recovery unit for phase separation treatment. The organic phase obtained through phase separation is returned to the original process system, while the aqueous phase obtained through phase separation is discharged or recycled after purification treatment.

10. The method for detecting the acidity of organic liquids based on the volume ratio-conductivity-pH compensation model according to claim 1, characterized in that, The organic stock solution is a weakly polar organic solvent in a non-buffered system, selected from at least one of alcohols, ketones, esters or alkanes; the organic stock solution does not contain electrolyte components or inorganic salt components that would cause the conductivity of the diluted mixed test solution to exceed 100 μS / cm.

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