CN-121672695-B - Method and system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis

CN121672695BCN 121672695 BCN121672695 BCN 121672695BCN-121672695-B

Abstract

The application relates to the technical field of high-salt waste liquid treatment, and discloses a method and a system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis. The method comprises the steps of collecting water quality characteristic parameters, calculating initial current density, starting electrodialysis, performing secondary fitting on a membrane resistance sequence in a sliding window to extract acceleration, early warning and descending when the threshold value is exceeded, performing reverse energization after descending, utilizing reverse migration of ions to strip scale layers to achieve online descaling, and calculating a health index based on accumulated reverse energization time and membrane resistance drift rate to dynamically adjust operation parameters. The application solves the technical problems that scaling on the membrane surface is difficult to early warn in real time and clean on line in the process of treating high-salt waste liquid by bipolar membrane electrodialysis.

Inventors

YU ZHENZHEN
LI YE
CHEN YUHUA
ZHANG YIZHANG
Ping Lingwen

Assignees

天津市滨海新区环境创新研究院

Dates

Publication Date: 20260508
Application Date: 20260210

Claims (9)

1. A method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis, which is characterized by comprising the following steps: S1, collecting water quality characteristic parameters of pretreated high-salt waste liquid, calculating initial current density and starting bipolar membrane electrodialysis; Step S2, performing quadratic polynomial fitting on a continuously collected real-time value sequence of the membrane resistance in a sliding time window, extracting a quadratic term coefficient of a fitting equation as membrane resistance acceleration, and generating an early warning signal and reducing current density when the membrane resistance acceleration exceeds a preset threshold value; Step S3, reducing the current to zero after the current density is reduced for a preset time, reversely applying reverse current with preset proportion of the current density after the current density is reduced for a preset time, stripping a scaling layer on the surface of the ion exchange membrane by using electrostatic repulsive force generated by reverse migration of ions, measuring membrane impedance values before and after reverse electrifying to calculate an impedance reduction rate as a cleaning effect, recovering the current to a numerical value before the current is reduced after the reverse electrifying is finished, and establishing a cycle of the current reducing operation and reverse electrifying cleaning to realize online descaling in the process of continuously preparing acid and alkali; The method comprises the steps of S4, calculating a membrane health index based on accumulated reverse power-on duration and membrane resistance baseline drift rate, adjusting operation parameters of the circulation period according to the membrane health index, calculating accumulated reverse power-on total duration according to accumulated reverse power-on times and each reverse power-on duration, calculating an electrochemical stress accumulation index according to the accumulated reverse power-on total duration, a reverse current absolute value, a membrane rated forward current and a membrane accumulated rated operation time, comparing the membrane health index with a health threshold value, comparing the membrane health index with the membrane health index according to a membrane health index calculation formula, and prolonging the circulation period falling current intensity when the membrane health index is lower than the health threshold value, wherein the membrane health index is the lowest membrane impedance value measured after each pulse cleaning, the contribution of a reversible scale layer only reflects the resistance of a membrane body and an irreversible pollution layer, the current membrane resistance baseline value is acquired, and the membrane resistance baseline drift rate is calculated according to the difference between the current membrane resistance baseline value and the initial membrane resistance baseline value divided by the initial membrane resistance baseline value and multiplied by 100%.
2. The method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis according to claim 1, wherein the step S1 comprises the following steps: collecting the total dissolved solid content, the calcium ion concentration, the magnesium ion concentration, the chemical oxygen demand and the conductivity of the pretreated high-salt waste liquid by an online ion chromatograph, and constructing a water quality characteristic data matrix; calculating a scaling risk coefficient according to a scaling risk coefficient calculation formula based on the calcium ion concentration and the magnesium ion concentration in the water quality characteristic data matrix; Measuring the limiting current density of the pretreated high-salt waste liquid through a three-electrode electrochemical workstation; And according to the water quality characteristic data matrix and the limiting current density, combining the target acid-base concentration and the preset treatment time, and reversely calculating the initial current density through a simultaneous equation set of ohm law and Faraday law.
3. The method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis according to claim 1, wherein the step S2 comprises: collecting a voltage value and a current value in the bipolar membrane electrodialysis process at preset sampling intervals, and calculating a membrane resistance real-time value according to ohm's law; obtaining a plurality of continuous real-time values of the membrane resistance in a sliding time window with a preset length, and constructing a membrane resistance time sequence; Performing quadratic polynomial fitting on the membrane resistance time sequence to obtain a fitting equation; And extracting a quadratic coefficient of the fitting equation as a membrane resistance acceleration, comparing the membrane resistance acceleration with a preset threshold, generating an early warning signal when the membrane resistance acceleration exceeds the preset threshold, calculating a danger coefficient according to the early warning signal, determining a current density reduction amplitude based on the danger coefficient, and executing a down-flow operation.
4. The method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis according to claim 1, wherein the step S3 of reducing the current to zero after the preset period of operation for reducing the current density comprises the steps of: After the current density is reduced for a preset time, linearly reducing the current from the value after current reduction to zero according to a preset slope rate; and standing for a preset stable period after the current is reduced to zero, and eliminating the electrode polarization effect.
5. The method for preparing acid and alkali by treating high-salt waste liquid by bipolar membrane electrodialysis according to claim 4, wherein the step S3 of reversely applying the reverse current of the preset proportion of the current density after the down-flow for a preset period of time comprises: Reversely applying current to a reverse current value corresponding to a preset proportion of the current density after current reduction according to a preset slope rate; maintaining the reverse current value for a preset reverse energization period; and after the preset reverse power-on duration is over, reducing the reverse current to zero according to a preset slope rate.
6. The method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis according to claim 5, wherein in the step S3, a membrane impedance value before and after reverse energization is measured to calculate an impedance decrease rate as a cleaning effect, current is restored to a value before current decrease after the reverse energization is finished, a cycle of current decrease operation and reverse energization cleaning is established to realize online descaling in the continuous preparation of acid and alkali, and the method comprises the following steps: before reverse current with preset proportion of current density after reverse current falling is applied, measuring a membrane impedance value as a membrane impedance value before cleaning by an electrochemical impedance spectroscopy technology; after the reverse current is reduced to zero, measuring a membrane impedance value as a membrane impedance value after cleaning through an electrochemical impedance spectrum technology; calculating an impedance drop rate according to the membrane impedance value before cleaning and the membrane impedance value after cleaning; after the reverse current is reduced to zero, the current is restored to a value before the current is reduced according to a preset slope rate; the operations of reducing the current density to run for a preset time period, reducing the current to zero, reversely applying the reverse current, and recovering the current to the value before the current reduction are repeatedly executed to form a circulation period.
7. A method system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis, which is characterized by being used for realizing the method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis according to any one of claims 1-6, wherein the method system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis comprises the following steps: The collection module is used for collecting the water quality characteristic parameters of the pretreated high-salt waste liquid, calculating the initial current density and starting bipolar membrane electrodialysis; The generation module is used for performing quadratic polynomial fitting on the continuously collected membrane resistance real-time value sequence in the sliding time window, extracting a quadratic term coefficient of a fitting equation as membrane resistance acceleration, and generating an early warning signal and reducing current density operation when the membrane resistance acceleration exceeds a preset threshold value; The measuring module is used for reducing the current to zero after the current density is reduced for a preset time period, reversely applying reverse current with preset proportion of the current density after the current density is reduced for a preset time period, stripping a scaling layer on the surface of the ion exchange membrane by using electrostatic repulsive force generated by reverse migration of ions, measuring the membrane impedance value before and after reverse electrifying to calculate the impedance reduction rate as a cleaning effect, recovering the current to a numerical value before the current is reduced after the reverse electrifying is finished, and establishing a cycle period of the current reduction operation and reverse electrifying cleaning to realize online descaling in the process of continuously preparing acid and alkali; the calculation module is used for calculating a membrane health index based on the accumulated reverse power-on duration and the membrane resistance baseline drift rate, and adjusting the operation parameters of the cycle period according to the membrane health index.
8. The system of claim 7, wherein collecting the water quality characteristic parameters of the pretreated high-salt waste solution, calculating the initial current density and starting bipolar membrane electrodialysis, comprises: collecting the total dissolved solid content, the calcium ion concentration, the magnesium ion concentration, the chemical oxygen demand and the conductivity of the pretreated high-salt waste liquid by an online ion chromatograph, and constructing a water quality characteristic data matrix; calculating a scaling risk coefficient according to a scaling risk coefficient calculation formula based on the calcium ion concentration and the magnesium ion concentration in the water quality characteristic data matrix; Measuring the limiting current density of the pretreated high-salt waste liquid through a three-electrode electrochemical workstation; And according to the water quality characteristic data matrix and the limiting current density, combining the target acid-base concentration and the preset treatment time, and reversely calculating the initial current density through a simultaneous equation set of ohm law and Faraday law.
9. The system of claim 8, wherein reducing the current to zero after the reduced current density operation for a preset period of time comprises: After the current density is reduced for a preset time, linearly reducing the current from the value after current reduction to zero according to a preset slope rate; and standing for a preset stable period after the current is reduced to zero, and eliminating the electrode polarization effect.

Description

Method and system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis Technical Field The application relates to the technical field of high-salt waste liquid treatment, in particular to a method and a system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis. Background The bipolar membrane electrodialysis technology decomposes the salt solution into corresponding acid and alkali under the drive of an electric field, and has wide application prospect in the field of recycling of high-salt waste liquid. In the process of preparing acid and alkali by treating high-salt waste liquid, the traditional bipolar membrane electrodialysis system enables anions and cations to migrate to corresponding electrodes respectively by applying a direct current electric field, and meanwhile, a hydrolytic separation layer of a bipolar membrane dissociates water molecules into hydrogen ions and hydroxide ions, so that salt-to-acid-base conversion is realized. Compared with the traditional chemical neutralization method, the technology has the advantages of low energy consumption, high product purity, no secondary pollution and the like, and has been applied to the fields of salt-containing wastewater treatment, organic acid preparation, industrial waste liquid recycling and the like. However, the existing bipolar membrane electrodialysis technology faces membrane pollution and scaling problems in the long-time continuous operation process, and restricts the industrialized popularization of the technology. When multivalent cations such as calcium ions, magnesium ions and the like in the high-salt waste liquid migrate to the cathode under the action of an electric field, insoluble salt scale layers are formed between the surface of the cation exchange membrane and anions such as carbonate radicals, sulfate radicals and the like, so that the membrane resistance continuously rises, the current efficiency is reduced, and the energy consumption is increased. The traditional coping method mainly comprises shutdown chemical cleaning and physical flushing, but the shutdown cleaning can cause production interruption and productivity loss, the use of chemical cleaning agents increases the operation cost and possibly damages the membrane materials, and the physical flushing has limited effect of removing the dense scale layer. More importantly, the prior art lacks a real-time early warning mechanism for the scaling state of the membrane surface, and remedial measures are often taken after the membrane resistance is obviously increased and the system performance is seriously deteriorated, so that the scaling layer is solidified and is difficult to remove, and the cleaning difficulty and the risk of membrane damage are greatly increased. Disclosure of Invention The application provides a method and a system for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis, which are used for solving the technical problems that scaling on the membrane surface is difficult to early warn in real time and clean on line in the process of treating the high-salt waste liquid through bipolar membrane electrodialysis, and improving the continuous operation stability of the system and the service life of the membrane. In a first aspect, the application provides a method for preparing acid and alkali by treating high-salt waste liquid through bipolar membrane electrodialysis, which comprises the following steps: S1, collecting water quality characteristic parameters of pretreated high-salt waste liquid, calculating initial current density and starting bipolar membrane electrodialysis; Step S2, performing quadratic polynomial fitting on a continuously collected real-time value sequence of the membrane resistance in a sliding time window, extracting a quadratic term coefficient of a fitting equation as membrane resistance acceleration, and generating an early warning signal and reducing current density when the membrane resistance acceleration exceeds a preset threshold value; Step S3, reducing the current to zero after the current density is reduced for a preset time, reversely applying reverse current with preset proportion of the current density after the current density is reduced for a preset time, stripping a scaling layer on the surface of the ion exchange membrane by using electrostatic repulsive force generated by reverse migration of ions, measuring membrane impedance values before and after reverse electrifying to calculate an impedance reduction rate as a cleaning effect, recovering the current to a numerical value before the current is reduced after the reverse electrifying is finished, and establishing a cycle of the current reducing operation and reverse electrifying cleaning to realize online descaling in the process of continuously preparing acid and alkali; and S4, calculating a membrane he