Low-temperature evaporation process for efficient treatment of high-salt high-concentration waste liquid and device

Abstract

The present application relates to the field of waste liquid discharge treatment, and particularly relates to a high-efficiency treatment method and device for high-salt and high-concentration waste liquid by low-temperature evaporation process. The method comprises the following steps: delivering the waste liquid to a water storage tank, detecting water quality parameters, and obtaining a sediment evaluation report; based on the sediment evaluation report, performing softening and sedimentation treatment on the waste liquid to obtain pretreated liquid; delivering the pretreated liquid to a low-temperature evaporation unit; performing evaporation and concentration treatment in the low-temperature evaporation unit to obtain concentrated liquid and deliver the concentrated liquid to a crystallization unit; performing crystallization treatment in the crystallization unit to obtain crystallization slurry; performing solid-liquid separation treatment on the crystallization slurry to obtain solid salt and mother liquor; judging that the mother liquor is harmless qualified water; returning the harmless qualified water to a production system as recycled water to complete zero-emission treatment operation. The present application realizes efficient waste liquid zero-emission treatment, reduces emission cost and improves emission treatment quality.

Description

Technical Field

[0001] This invention relates to the field of wastewater discharge treatment, and in particular to a method and apparatus for the efficient treatment of high-salt and high-concentration wastewater using a low-temperature evaporation process. Background Technology

[0002] Low-temperature evaporation technology, as an energy-saving and low-scaling concentration treatment method, can effectively concentrate high-salt, high-concentration waste liquids under low temperature and negative pressure environments, thereby reducing waste liquid volume, lowering the risk of scaling, and ensuring that heat-sensitive components do not undergo thermal decomposition. However, in practical applications, the complex composition of high-salt, high-concentration waste liquids can still lead to problems such as local supersaturation, uneven crystal precipitation, scaling on heat exchange surfaces, and low salt recovery efficiency during the evaporation process, affecting system stability and operating efficiency. Furthermore, the high-concentration liquid after evaporation and concentration still needs to undergo effective crystallization separation to achieve solid salt recovery and mother liquor recycling, avoid secondary pollution, and ensure the achievement of zero-emission goals.

[0003] Existing methods for treating high-salt waste liquids mostly rely on single concentration or chemical treatment technologies, lacking systematic control and intelligent management of the entire waste liquid process. This makes it impossible to ensure concentration efficiency while simultaneously achieving uniform crystallization, mother liquor reuse, and controllable solid salt product quality. Furthermore, the lack of real-time monitoring and precise control of parameters such as supersaturation, crystallization priority, and circulation conditions during the treatment process leads to high energy consumption and operating costs. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method and apparatus for the efficient treatment of high-salt, high-concentration waste liquid using a low-temperature evaporation process, thereby solving at least one of the aforementioned technical problems.

[0005] To achieve the above objectives, the present invention provides a method for the efficient treatment of high-salt, high-concentration waste liquid using a low-temperature evaporation process, comprising the following steps: Step S1: The waste liquid is transported to a storage tank for water quality parameter testing to obtain a sediment assessment report; Step S2: Based on the precipitate assessment report, the waste liquid is softened and precipitated to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. Step S3: Evaporation and concentration are carried out in the low-temperature evaporation unit to obtain concentrated liquid, which is then transported to the crystallization unit; Step S4: Perform crystallization treatment in the crystallization unit to obtain crystallized slurry; Step S5: Perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

[0006] This specification provides an efficient treatment apparatus for high-salt, high-concentration waste liquid using a low-temperature evaporation process, for performing the efficient treatment method for high-salt, high-concentration waste liquid using the low-temperature evaporation process described above, comprising: The water quality monitoring module is used to transport waste liquid to a storage tank, detect water quality parameters, and obtain a sediment assessment report. The softening and settling module is used to soften and settle the waste liquid based on the settling assessment report to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. The evaporation and concentration module is used to perform evaporation and concentration in the low-temperature evaporation unit to obtain a concentrated liquid and transport it to the crystallization unit. The crystallization module is used to perform crystallization processing in the crystallization unit to obtain a crystallized slurry. The evaluation module is used to perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; and return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

[0007] The specific beneficial effects of this invention are as follows: by concentrating waste liquid into a storage tank and conducting water quality parameter testing, homogenized management can be achieved, and the Ca content can be accurately controlled. 2+ Mg 2+ Key indicators such as COD are assessed. The precipitate assessment report provides the supersaturation index, potential precipitate amount, and precipitation risk, providing a basis for softening treatment dosing and operational control. This helps reduce the risk of scaling in the evaporation and crystallization sections, improves operational safety, and the softening precipitation treatment effectively removes high-hardness ions, reduces waste liquid supersaturation, and reduces scale formation. The clarity of the mother liquor is improved, and the uniformity of the concentrate is enhanced. This step reduces the risk of scaling in the evaporation section, improves heat transfer efficiency, extends equipment life, and reduces energy consumption and maintenance frequency, ensuring the safe and stable operation of the low-temperature evaporation section and supporting the zero-emission target. Low-temperature negative pressure evaporation can lower the boiling point of water, avoiding thermal decomposition and rapid scaling of high-salt waste liquid. Evaporation and concentration significantly reduce the volume of waste liquid and increase the solute concentration, providing a high-concentration, controllable solution for the crystallization unit.

[0008] By controlling seed crystal addition, temperature gradient, and circulation conditions, preferential precipitation of the main precipitate and uniform crystal growth are achieved. The crystals are concentrated in size and have regular morphology, improving crystallization efficiency and solid recovery rate while reducing mother liquor turbidity and suspended particle content. Solid-liquid separation efficiently separates the crystallization slurry into solid salt and mother liquor. Drying treatment ensures the solid salt moisture content is ≤5%, guaranteeing product stability. The mother liquor, after testing, is harmless and reusable, reducing fresh water consumption and achieving a closed-loop water resource cycle. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the steps of a low-temperature evaporation process for the efficient treatment of high-salt, high-concentration waste liquid according to the present invention. Figure 2 This is a detailed flowchart illustrating the implementation steps of step S1. Figure 3 This is a flowchart illustrating the detailed implementation steps of step S2.

[0010] Figure 4 This is a density curve for the concentration and evaporation stage in step S3. Figure 5 This is a curve for determining the concentration endpoint in step S3; Figure 6 This is a schematic diagram illustrating the conditions for crystallization in a supersaturated solution. Detailed Implementation

[0011] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0012] This application provides a method and apparatus for the efficient treatment of high-salt, high-concentration waste liquid using a low-temperature evaporation process. The executing entities of the method and apparatus for the efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process include, but are not limited to, mechanical equipment, data processing platforms, cloud server nodes, and network upload devices that can be considered as general computing nodes in this application. The data processing platform includes, but is not limited to, at least one of an audio-visual management system, an information management system, and a cloud-based data management system.

[0013] Please see Figures 1 to 6 This invention provides a method for the efficient treatment of high-salt, high-concentration waste liquid using a low-temperature evaporation process, comprising the following steps: Step S1: The waste liquid is transported to a storage tank for water quality parameter testing to obtain a sediment assessment report; Step S2: Based on the precipitate assessment report, the waste liquid is softened and precipitated to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. Step S3: Evaporation and concentration are carried out in the low-temperature evaporation unit to obtain concentrated liquid, which is then transported to the crystallization unit; Step S4: Perform crystallization treatment in the crystallization unit to obtain crystallized slurry; Step S5: Perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

[0014] In the embodiments of the present invention, see Figure 1 This is a schematic flowchart illustrating the steps of a method for efficiently treating high-salt, high-concentration waste liquid using a low-temperature evaporation process according to the present invention. In this example, the steps of the method for efficiently treating high-salt, high-concentration waste liquid using a low-temperature evaporation process include: Step S1: The waste liquid is transported to a storage tank for water quality parameter testing to obtain a sediment assessment report; In this embodiment, high-salt / high-concentration waste liquid is transported to a homogenized storage tank via corrosion-resistant pipelines. The pipelines are typically made of PPH, PVDF, or duplex stainless steel to withstand corrosive environments with chloride ion concentrations as high as 20,000 mg / L. The transfer pumps are fluoropolymer-lined magnetic pumps or corrosion-resistant centrifugal pumps, with flow rates controlled at 3-15 m³ / h. 3 The flow rate is controlled by frequency conversion to ensure stability, preventing salt deposition due to excessively low flow rates or shear bubbles due to excessively high flow rates. After the waste liquid enters the storage tank, a mechanical agitator is activated, typically a propeller-type or frame-type agitator, with the speed controlled at 80-120 rpm to create uniform turbulence within the tank (Reynolds number > 10). 4 To ensure thorough mixing of ions and solutes, the wastewater was then tested for water quality parameters, including conductivity (0-200 mS / cm), pH (accuracy ±0.02), temperature (±0.1℃), turbidity (0-4000 NTU), COD (0-10000 mg / L), and calcium and magnesium ion concentrations (using EDTA titration and calibrated with ICP-OES). Data was collected once per minute, continuously monitored for at least 120 minutes, and data from the stable phase was used to generate wastewater information. Combining conductivity, pH, hardness, and COD values, the supersaturation index and potential precipitation amount of various precipitates were calculated using water quality characteristic matrix analysis and thermodynamic models, resulting in a precipitate assessment report, including precipitate types, precipitation risks, and quantitative indicators.

[0015] Step S2: Based on the precipitate assessment report, the waste liquid is softened and precipitated to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. In this embodiment, based on the precipitate type and concentration determined in the precipitate assessment report, a suitable softening agent, such as sodium carbonate, sodium hydroxide, or lime slurry, is selected to soften and precipitate the waste liquid. The agent solution is prepared in a storage tank or independent reaction vessel, with the concentration calculated based on the waste liquid volume. The dosage is generally equal to the Ca concentration in the waste liquid. 2+ Mg 2+ The amount of precipitate added is 1.05 times the theoretical precipitate volume to ensure a complete reaction. Continuous, quantitative addition is used, with a gradual addition time of 5-20 minutes, while low-speed stirring (approximately 80-120 rpm) maintains uniform liquid dispersion. During the reaction, the pH range is controlled online; for example, CaCO3 precipitation is suitable at pH 7.0-7.5, and Mg(OH)2 precipitation is suitable at pH 9.0-9.5 to improve precipitation efficiency. The reaction time is maintained at 20-40 minutes to allow the precipitate crystals to grow sufficiently. The softened liquid is then subjected to solid-liquid separation, filtering out some coarse particles to improve the clarity of the mother liquor. The mother liquor is the pretreatment liquid. 2+ With Mg 2+The concentration was significantly reduced, and the supersaturation index was close to or below 0. The pretreatment solution was fed into the low-temperature evaporation unit via a corrosion-resistant transfer pump.

[0016] Step S3: Evaporation and concentration are carried out in the low-temperature evaporation unit to obtain concentrated liquid, which is then transported to the crystallization unit; In this embodiment, after the pretreated liquid enters the low-temperature evaporation section, the pressure in the evaporation chamber is controlled at -0.08 to -0.095 MPa by a vacuum pump, lowering the boiling point of water to 45-65℃ and reducing the risk of thermal decomposition and scaling. A circulation pump maintains a liquid flow rate of 1.5-2.5 m / s to enhance heat exchange and prevent localized deposition. The heating medium is hot water or steam, and the heat exchange surface temperature is controlled at 55-70℃. The evaporation rate is typically 0.5-2 t / h. An online density meter measures the density of the concentrated liquid with an accuracy of ±0.001 g / cm³. 3 The degree of solution saturation is calculated by combining conductivity and supersaturation index. When concentrated to 95-98% of the solubility limit of the waste liquid, the density generally rises to 1.22-1.28 g / cm³. 3 The SI value is approximately 0-0.2. After reaching the concentration endpoint, the concentrate is pumped into the crystallization unit to prevent supersaturation and crystallization blockage in the evaporation section. Step S4: Perform crystallization treatment in the crystallization unit to obtain crystallized slurry; In this embodiment, seed crystals are selected based on the ionic composition and supersaturation of the concentrate, and the addition conditions are controlled. The seed crystal particle size range is 100-300 μm, and the addition amount accounts for 3-8% of the concentrate mass. A continuous quantitative addition method is adopted, with the addition time controlled in a gradual operation over 5-20 minutes. The crystallization temperature gradient is controlled within the range of 60-40℃, with a cooling rate of 0.5-1℃ / min; the circulation ratio is 15-30 times the evaporation rate to ensure uniform crystal suspension; the stirring intensity is controlled at 100-150 rpm to prevent crystal breakage. Crystallization is maintained for 2-6 hours to allow the crystals to grow fully to 300-800 μm, the supersaturation gradually decreases, and the slurry becomes clear. The crystallization state is monitored by online density, conductivity, and particle size analysis to ensure that the main crystallization sequence is consistent with theoretical predictions, and that the crystal particles have regular morphology, which is beneficial for subsequent solid-liquid separation. A crystalline slurry is formed with a solid content of approximately 20-35%.

[0017] Step S5: Perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

[0018] In this embodiment, the crystallized slurry undergoes solid-liquid separation using a centrifuge or plate and frame filter press. The centrifuge speed is controlled at 3000-4000 rpm, and the turbidity of the filtrate is ≤100 NTU; the filter press pressure is 0.6-1.0 MPa, and the filter cake thickness is 20-40 mm. The separated solid salt filter cake has a moisture content of approximately 15-25%, and is then subjected to low-temperature hot air vacuum drying at a temperature of 80-90℃ and a vacuum degree of -0.06 to -0.09 MPa for 2-4 hours, reducing the moisture content of the solid salt to ≤5%, thus obtaining a dried solid salt product. The solid salt is analyzed to confirm whether it is a single salt or contains heavy metals. If it is a mixed salt or contains excessive heavy metals, it is packaged and disposed of according to hazardous waste regulations. The mother liquor undergoes particle concentration testing. When the suspended particles are below the preset threshold (≤100 mg / L) and the COD is ≤50 mg / L, it is determined to be harmless and qualified water. It is then recycled back to the production process via a transfer pump, achieving a closed-loop water resource cycle and completing the goal of zero discharge treatment of high-salt / high-concentration waste liquid.

[0019] In this embodiment, see Figure 2 The diagram below illustrates the detailed implementation steps of step S1. In this embodiment, the detailed implementation steps of step S1 include: Waste liquid is transported to a storage tank via pipeline for continuous stirring and water quality parameter testing to extract waste liquid information, including conductivity, pH value, temperature, turbidity, COD, and calcium and magnesium ion concentration. Water quality characteristics are analyzed based on waste liquid information to generate a water quality characteristic matrix; Based on the water quality feature matrix, high-hardness scale-forming ions are identified to determine the types of precipitates. The supersaturation index and potential sediment amount of various precipitates are calculated based on the waste liquid information; water quality assessment is conducted based on the precipitate type, supersaturation index, and potential sediment amount to obtain a precipitate assessment report.

[0020] In this embodiment, the waste liquid is transported from the production end to the homogenization tank via a corrosion-resistant, sealed pipeline. The pipeline material is typically PPH, PVDF, or duplex stainless steel 2205 to withstand corrosive environments with chloride ion concentrations exceeding 20,000 mg / L. The transfer pump is a corrosion-resistant magnetic drive pump or a fluoropolymer-lined centrifugal pump, with a flow rate controlled at 3-15 m³ / L. 3 The flow rate is maintained between 100 m / h and 120 m / h using frequency conversion adjustment to prevent sedimentation due to excessively low flow rate or shear bubbles due to excessively high flow rate. After the waste liquid enters the storage tank, a mechanical agitator is activated, typically a propeller-type or frame-type agitator, with the speed controlled at 80-120 rpm to create a uniform turbulent flow state within the tank (Reynolds number greater than 10). 4To ensure uniform dispersion of salts and organic matter, the storage tank is equipped with a temperature monitoring device to stabilize the liquid temperature within the range of 25-40℃, approximating the conditions before subsequent evaporation. Continuous water quality parameter monitoring is then performed, collecting data on conductivity (0-200 mS / cm), pH (accuracy ±0.02), temperature (±0.1℃), turbidity (0-4000 NTU), COD (0-10000 mg / L), and calcium and magnesium ion concentrations. Calcium and magnesium ions are determined using EDTA complexometric titration and calibrated with ICP-OES data. The sampling frequency is set to once per minute, with continuous monitoring for at least 120 minutes. The average value during the stable phase is selected as the basis for analysis, forming a complete waste liquid information dataset. Smoothing is performed using a moving average method (window of 5-10 data points), and conductivity is converted to the 25℃ standard state. Derivative indicators are then calculated based on the detection data, such as estimating total dissolved solids (TDS) using conductivity (conversion factor 0.6-0.7), and based on Ca... 2+ With Mg 2+ Calculate total hardness (as CaCO3) based on concentration, estimate alkalinity based on pH and carbonate equilibrium, and calculate ionic strength I = 0.5ΣCiZi 2 In high-salt wastewater, the ionic strength is typically greater than 0.1 mol / L, indicating a strong electrolyte environment. To eliminate dimensional differences, all parameters were Z-score normalized, and a water quality characteristic matrix W=[EC, pH, T, Tur, COD, Ca] was constructed. 2+ Mg 2+ [, TDS, I]. If the effects of evaporation and concentration need to be considered, the corresponding parameters can be calculated according to the concentration ratios of 1.0, 1.3, and 1.5 respectively, and a multi-condition matrix can be formed.

[0021] The ion product Q value of each potential precipitate was calculated based on water quality characteristic matrix data and compared with its solubility product constant Ksp. Typical salts include CaCO3 (Ksp≈3.3×10⁻⁶). -9 ), CaSO4 (Ksp≈2.4×10) -5 ) and Mg(OH)2 (Ksp≈5.6×10 -12 For example, when the evaporation concentration ratio reaches 1.5, Ca 2+ When the concentration increases from 8000 mg / L to approximately 12000 mg / L, and the pH increases to above 8.5, Q(CaCO3) is significantly greater than Ksp, indicating that calcium carbonate preferentially precipitates; if the pH increases to above 9 and Mg... 2+Magnesium hydroxide tends to precipitate when the concentration is above 5000 mg / L. To improve the accuracy of the judgment, thermodynamic equilibrium calculations can be performed to simulate the mineral saturation state under different temperatures (30-60℃) and ionic strength conditions. Generally, the precipitation order is CaCO3 preferentially, followed by CaSO4, and then Mg(OH)2. The main precipitate types and their formation condition ranges should be determined.

[0022] Further calculations were performed on the supersaturation index SI for each precipitate: SI = log(Q / Ksp). A SI value greater than 0 indicates a supersaturated solution, with a higher value indicating a stronger driving force for precipitation. For example, under a 1.5-fold concentration, if the calculated results are SI(CaCO3) = 0.85, SI(CaSO4) = 0.32, and SI(Mg(OH)2) = -0.1, then calcium carbonate is the primary source of scaling risk. Subsequently, the potential precipitate volume was estimated based on material balance, and the theoretical precipitation mass was calculated using m = (C0 - Ceq) × V. If the single batch processing volume is 10 m³ / s... 3 The predicted CaCO3 precipitation amount can reach 80-120 kg. This is based on an operating temperature of 50-70℃, a circulation velocity of 1.5-2.5 m / s, and a heat flux of 20-40 kW / m². 2 Using various operating parameters, assess the impact of sediment on the decrease in heat transfer coefficient (typically 10-30%). Compile a sediment assessment report, including statistical analysis of water quality parameters, characteristic matrix analysis results, comparison of SI values ​​for each sediment, and prediction of potential sedimentation volume. Provide operational control recommendations, such as maintaining pH within the range of 7.0-7.5, keeping scale inhibitor dosage at 5-15 mg / L, and controlling the concentration ratio below 1.5.

[0023] In this embodiment, see Figure 3 The diagram below illustrates the detailed implementation steps of step S2. In this embodiment, the detailed implementation steps of step S2 include: Based on the precipitate assessment report, acid-base neutralization analysis was performed to determine the type of softening agent. Calculate the dosage based on the precipitate assessment report; Decision analysis is conducted based on the type and dosage of softening agent to obtain the dosing strategy; Based on the dosing strategy, the dosing metering pump set adds chemicals to the water storage tank for softening and sedimentation treatment; The precipitate is removed by the solid-liquid separation unit to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit.

[0024] In this embodiment, a comprehensive analysis is conducted on the main precipitate types, supersaturation index (SI), and potential precipitate amounts listed in the report, with a focus on the formation conditions of high-hardness salts such as CaCO3, CaSO4, and Mg(OH)2. If the report shows that CaCO3 is the dominant scale and the SI value is greater than 0.8, it indicates that the alkalinity is too high or the pH is in the weakly alkaline range (usually 8.2-9.0), requiring acidification to reduce the carbonate concentration; if Mg... 2+ If the content is high and the pH is low (6.5-7.0), alkalization can be used to convert it into Mg(OH)2 precipitate. The current alkalinity (calculated as CaCO3, generally in the range of 1000-5000 mg / L) and buffer capacity of the waste liquid are measured, and the pH adjustment sensitivity range is determined through titration curves. Acid-base neutralization experiments are usually conducted on a beaker scale (1-2 L sample), using 0.5 mol / L HCl or 10% NaOH solution added stepwise, adjusting the pH by 0.2 units each time, and recording the CaCO3 concentration. 2+ Mg 2+ Residual concentration changes. The optimal precipitation range is determined by plotting pH-hardness removal rate curves. For example, CaCO3 shows a significant reduction in supersaturation tendency at pH 7.0-7.5, while Mg(OH)2 can achieve a precipitation rate of over 90% above pH 9.5. If CaSO4 is the main risk substance, pH adjustment is usually not required; instead, sodium carbonate or phosphate is added for conversion and precipitation. The amount of Ca to be removed is determined based on the potential precipitation data in the assessment report. 2+ or Mg 2+ Total mass, for example if Ca 2+ The concentration was 12000 mg / L, and the treatment volume was 10 m³. 3 The total calcium mass is approximately 120 kg. If Na₂CO₃ is used to precipitate Ca... 2+ According to the reaction formula Ca 2+ + CO3 2- → Calculations using CaCO3↓ show a theoretical molar ratio of 1:1, combined with the molar mass of Na2CO3 being 106 g / mol and Ca... 2+ With a molar mass of 40 g / mol, the theoretical dosage is approximately 318 kg. In practical engineering, considering factors such as reaction efficiency and uneven stirring, a safety factor of 5-10% is typically added. If lime slurry is used to remove Mg... 2+ According to Mg 2+ + 2OH - → Calculation of Mg(OH)2↓, combined with Mg in the waste liquid 2+Calculate the actual dosage based on the concentration (e.g., 5000 mg / L) and lime purity (90%). During the experimental verification phase, small-scale beaker tests (JarTest) are typically conducted to test sedimentation time, supernatant turbidity (target <50 NTU), and residual hardness under different reagent concentrations (0.9, 1.0, and 1.1 times the theoretical amount) to select the optimal dosage ratio.

[0025] Analyze the range of waste liquid flow rate variation (e.g., 3-10 m³). 3 / h) and water quality fluctuation range (Ca 2+ Fluctuations ±10%). If the water quality is relatively stable, a continuous proportional dosing method can be used to maintain a fixed ratio between the reagent flow rate and the waste liquid flow rate. For example, for every 1 m³ treated... 3 Add 30 kg of Na₂CO₃ to the waste liquid. If the water quality fluctuates significantly, a staged adjustment strategy should be adopted, dynamically adjusting the dosage based on online hardness test data. The dosing strategy also needs to consider the reaction time. Generally, precipitation reactions require 20-40 minutes for thorough mixing and crystal nucleation, therefore, the effective residence time in the storage tank must be ensured to be no less than 30 minutes. The stirring intensity should be controlled at around 100 rpm to promote uniform reaction while avoiding excessive shear that could damage crystal growth. For high-magnesium waste liquid, a two-stage dosing strategy is often adopted: first, adjust the pH to 8.5 to remove some calcium carbonate, then raise it to above 9.5 to remove Mg(OH)₂, in order to reduce the increased chemical consumption caused by co-precipitation.

[0026] According to the determined dosing strategy, the metering pump unit is started to add the reagent to the storage tank in a metered manner. The metering pump adopts a corrosion-resistant diaphragm structure, with a flow rate adjustment range of 0.5-5 m³ / h. 3 / h, metering accuracy ±1%. The reagent solution concentration is configured according to calculation results, for example, preparing a 10% mass fraction sodium carbonate solution or a 5% lime slurry suspension. The dosing port is located downstream of the stirrer to utilize turbulent flow for rapid mixing. During the dosing process, the pH change curve is monitored in real time, and the pH is controlled within the set range (e.g., 7.2±0.1 or 9.5±0.2). During the reaction stage, stirring is maintained for 30-45 minutes to allow the precipitate to fully form and grow. A small amount of flocculant (e.g., polyacrylamide, 1-3 mg / L) can be added appropriately to promote particle aggregation and increase the settling velocity.

[0027] After the softening and sedimentation reaction is complete, the mixture is introduced into a solid-liquid separation unit for precipitate removal. Gravity settling tanks or inclined plate sedimentation tanks are commonly used, with the surface loading controlled at 0.8-1.2 m. 3 / m 2The residence time is approximately 60-90 minutes, allowing CaCO3 or Mg(OH)2 particles to settle naturally. For finer particles or higher concentrations, a plate and frame filter press or horizontal screw centrifuge can be used for enhanced separation, with a centrifugation speed generally between 3000-4000 rpm. The sludge after separation has a moisture content of approximately 60-75% and can be periodically transported for disposal. The supernatant is the pretreatment liquid, and its Ca... 2+ Mg 2+ The concentration decreased significantly, and the supersaturation index approached or was less than 0, creating low-scaling conditions for low-temperature evaporation. Finally, the pretreated liquid was transported to the low-temperature evaporation unit via a corrosion-resistant transfer pump for concentration treatment under conditions of evaporation temperature of 50-65℃ and vacuum degree of -0.08 to -0.095 MPa.

[0028] In this embodiment, step S3 includes the following steps: Adjust the low-temperature evaporation unit to a negative pressure environment, set the evaporation temperature to the target range, start the evaporation and concentration program to evaporate and concentrate the pretreatment liquid, obtain the concentrate, and simultaneously detect the density and supersaturation of the concentrate. The concentration endpoint is set as the solubility limit of the waste liquid. The concentration endpoint is determined based on the concentration and supersaturation of the concentrate. When a concentration endpoint signal is detected in the current solution, the concentrate is transported to the crystallization unit.

[0029] In this embodiment, air is drawn from the evaporation chamber by a vacuum pump unit, gradually reducing the internal pressure to the range of -0.08 to -0.095 MPa, corresponding to an absolute pressure of approximately 5-20 kPa. Under this negative pressure condition, the boiling point of water can be reduced to 45-65℃, thereby achieving low-temperature evaporation and reducing the risk of scaling and thermal decomposition in a high-salt environment. After the negative pressure is established, the circulation pump is started to create a flow velocity of 1.5-2.5 m / s for the liquid in the evaporator heat exchange tubes, thereby improving heat transfer efficiency and reducing local deposition. Using steam or hot water as a heat source, the heat exchange surface temperature is controlled within the range of 55-70℃, and the evaporation temperature is set at 50-65℃ based on the characteristics of the waste liquid. During the evaporation process, water continuously vaporizes and is recovered by the condenser, and the salt content of the concentrated liquid gradually increases. To monitor the concentration status in real time, an online density meter (range 1.0-1.4 g / cm³) is used. 3 Accuracy ±0.001 g / cm 3 Continuous monitoring of the concentrate density change was performed, and the density was converted to standard state density using a temperature correction formula. The supersaturation index (SI) was calculated based on the solubility product constant of the main salts in the solution and the current ion concentration. When the SI gradually approaches 0 or slightly exceeds 0, it indicates that the crystallization critical point is approaching. Typically, when the concentration ratio reaches 1.8-2.5 times, the solution density may increase from 1.05 g / cm³. 3 Rising to 1.20 g / cm³ 3In this stage, it is necessary to increase the monitoring frequency (record data every 2-5 minutes) to ensure that the concentration process is stable and controllable.

[0030] To ensure maximum volume reduction during evaporation while avoiding premature crystallization and blockage, the concentration endpoint needs to be predetermined. This endpoint is determined based on the solubility limits of the main inorganic salts (such as NaCl, Na₂SO₄, or complex salts) in the waste liquid. The solubility limits of the main salts are determined by consulting solubility curves or conducting experimental measurements at the target evaporation temperature (e.g., 60°C). For example, the solubility of NaCl at 60°C is approximately 390 g / L. When the total dissolved solids in the solution approach 95-98% of this value, the concentration endpoint control range is defined. In practice, a small-scale experiment can be conducted to gradually evaporate the sample until initial crystallization occurs, recording the density value at this point (e.g., 1.23 g / cm³). 3 The corresponding TDS value (approximately 350-380 g / L) is used as the endpoint reference value. Simultaneously, a supersaturation index control strategy is employed, keeping the SI value between 0 and 0.2 as a safe upper limit to prevent large-scale crystallization within the evaporation chamber. The endpoint setting also needs to consider heat transfer safety margins, typically maintaining a 2-5% safety margin before reaching the theoretical solubility limit to prevent premature precipitation caused by localized high-temperature areas.

[0031] During the evaporation process, density and supersaturation index are continuously and dynamically monitored. The evaporation is completed when the online density meter displays a density value reaching a preset endpoint range (e.g., 1.22-1.24 g / cm³). 3 Simultaneously, when the SI value of the main salts is calculated to be greater than or equal to 0, the concentration endpoint signal is determined to have occurred. To avoid false judgments, this state is typically required to remain stable for at least 5-10 minutes, and it is confirmed that there are no abnormal fluctuations in evaporation temperature and pressure (pressure fluctuation ≤ ±2 kPa, temperature fluctuation ≤ ±1℃). Once the endpoint conditions are confirmed, the heating power is gradually reduced to slow down the evaporation intensity, and then the concentrate transfer pump is started to transport the high-concentration solution to an independent crystallization unit. During the transport process, the flow rate is controlled at 1-3 m / s. 3 Within a certain range ( / h), flow impact can be prevented from causing crystallization in the pipeline. After entering the crystallization unit, further cooling (e.g., from 60℃ to 35-40℃) or controlled evaporation flash evaporation can promote uniform salt precipitation. By precisely controlling the endpoint parameters during the evaporation stage, the crystallization process can be ensured to be completed within a dedicated space, avoiding scaling on the evaporation heat exchange surface, improving overall operational stability and salt recovery efficiency, thereby achieving the goal of reducing and achieving zero discharge of high-salt / high-concentration wastewater.

[0032] In this embodiment, during the evaporation and concentration process, the water vapor generated by the evaporation and concentration is detected; the water vapor is cooled by a condenser to obtain condensate; the conductivity and COD of the condensate are calculated; the conductivity and COD are tested for dual indicators; if the test results meet the standards, the condensate is returned to the production system as recycled water; if the test results do not meet the standards, it is treated by adsorption with activated carbon.

[0033] In this embodiment, during the low-temperature negative pressure evaporation and concentration process, in addition to monitoring the concentrate, continuous detection of the water vapor generated by evaporation is required to determine whether volatile components are entrained into the condensation section with the steam. The evaporation temperature is typically controlled at 50-65℃, and the absolute pressure is maintained in the range of 5-20 kPa. Under these conditions, the water vaporization rate is generally 0.5-2.0 t / h (depending on the processing scale). A steam sampling port and an online monitoring interface are installed at the top of the evaporation chamber to detect the steam temperature (±0.5℃), pressure (±1 kPa), and moisture content. To prevent droplet entrainment, a wire mesh demister or hydrocyclone separator is typically installed at the evaporation chamber outlet to achieve a gas-liquid separation efficiency of over 99% and a droplet size controlled to ≤5 μm. Online steam monitoring focuses on the presence of volatile organic compounds or light components such as ammonia nitrogen, which can be confirmed through an online TOC monitor or gas phase condensation sampling analysis. If the initial COD concentration in the waste liquid is high (e.g., 5000-10000 mg / L), special attention should be paid to whether low-boiling-point organic matter is carried out with the steam. The steam detection frequency is generally set to record operating parameters once every 5 minutes, and increased to once per minute in the initial stage of operation or during water quality fluctuations to ensure that the water vapor generated during the evaporation stage has a stable composition and no obvious pollutant entrainment.

[0034] The water vapor produced by evaporation enters the condenser for heat exchange and cooling. The condenser can be a shell-and-tube or plate type structure, and the cooling medium is circulating cooling water or low-temperature softened water. The inlet water temperature is generally 20-30℃, and the outlet water temperature is controlled at 30-40℃. Under negative pressure, the steam condensation temperature is usually 40-60℃, which is achieved by controlling the cooling water flow rate (e.g., 5-15 m³ / h). 3 (h) Adjust the condensation efficiency to ensure complete liquefaction of the steam. The condenser heat exchange area is designed based on the evaporation rate, and the unit heat transfer coefficient is typically 1500-2500 W / m². 2 • K range. After condensation, condensate is formed, typically between 35-45℃, and is collected in a condensate storage tank through a closed pipeline. To prevent secondary contamination, the condensate pipeline should be made of stainless steel or corrosion-resistant materials and maintained under slight negative pressure or in a closed state. The condensate production rate is usually roughly the same as the evaporation rate; for example, 1 t / h of water evaporation corresponds to approximately 1 t / h of condensate production. A stirring device is installed in the condensate storage tank, running at a low speed (approximately 50 rpm) to prevent temperature stratification.

[0035] Water quality testing is conducted immediately after condensate enters the storage tank. Conductivity is measured using an online conductivity meter with a range of 0-2000 μS / cm and an accuracy of ±1%. Under normal circumstances, the conductivity of pure steam condensate should be below 50 μS / cm; however, if salt spray is present, it may rise above 200 μS / cm. COD is then measured using a rapid digestion spectrophotometric method with a range of 0-500 mg / L and a testing cycle of approximately 20 minutes. For zero-discharge reuse requirements, the standard for condensate reuse is typically set at conductivity ≤100 μS / cm and COD ≤50 mg / L (specific indicators can be determined based on production water requirements). When both conductivity and COD are below the set thresholds, and the results are stable for three consecutive tests (fluctuation ≤±5%), the water quality is considered compliant. If either indicator exceeds the standard, for example, conductivity rises to 150 μS / cm or COD reaches 120 mg / L, a pollution risk is considered. To improve accuracy, TOC or ammonia nitrogen retesting may be necessary to confirm the source of pollution.

[0036] Once the dual-indicator test results meet the standards, the condensate is returned to the production process via a transfer pump as recycled water, for example, for equipment cleaning or circulating cooling water replenishment. The recycling flow rate is automatically matched according to the evaporation rate, typically controlled within the range of 0.5-2 t / h. If the test results do not meet the standards, the condensate is introduced into the activated carbon adsorption unit for further treatment. The activated carbon column generally uses granular activated carbon with a particle size of 1-3 mm, an iodine value ≥900 mg / g, a packing height of 1.5-2.0 m, an empty bed contact time controlled at 20-40 minutes, and a filtration flow rate of 5-10 m / h. During the adsorption process, organic pollutants are retained through physical adsorption, and COD can be reduced by more than 50-80%. After treatment, the conductivity and COD are tested again, and the condensate can only be returned to the production process after confirming that it meets the recycling standards. If the activated carbon adsorption is close to saturation (the outlet COD removal rate drops below 30%), regeneration or replacement is required.

[0037] In this embodiment, the specific steps of step S4 are as follows: Calculate the conductivity and different ion concentrations of the concentrate to obtain the current solution state; Based on the current solution state, crystallization analysis is performed to determine the main crystal types and crystallization priority order; Seed crystals are screened according to the main crystallization type to obtain seed crystal information; the seed crystal information includes the seed crystal size range, dosage, and dosage type. Based on the crystallization priority order, the temperature gradient, circulation rate, and stirring intensity of the crystallization unit are set to obtain the control parameters; Based on the control parameters and seed crystal information, the crystallization unit is driven to perform crystallization treatment to obtain crystallization slurry.

[0038] In this embodiment, a detailed water quality analysis was performed. The conductivity of the concentrate was measured using an online conductivity meter, typically with a range of 0-300 mS / cm and an accuracy of ±1%. During the high-salt concentration stage, the conductivity may reach 120-250 mS / cm, corresponding to a total dissolved solids (TDS) of 250-400 g / L. Using a temperature correction formula, the measured conductivity was converted to a 25°C standard value to eliminate the influence of temperature on conductivity. Subsequently, ion chromatography or ICP-OES was used to analyze the Na+ concentration. + Cl - SO4 2- Ca 2+ Mg 2+ Quantitative analysis of major ions is performed, typically every batch or every 2 hours. In a typical high-salt concentrate, Na... + Concentrations can reach 80-120 g / L, Cl - Concentration 100-180 g / L, SO4 2- Concentration 20-60 g / L. Ionic strength I = 0.5ΣCiZi is calculated based on the concentration of each ion. 2 At high concentrations, the I value can exceed 2.0 mol / L, indicating that the solution is in a highly non-ideal state. (Binding density, e.g., 1.22-1.28 g / cm³) 3 The temperature (50-60℃) is used to comprehensively determine whether the current solution is approaching or entering the supersaturated region.

[0039] After determining the ionic composition of the concentrate, the supersaturation index (SI) is calculated based on the solubility and ion product of each salt at the current temperature to determine the crystallization trend. For example, at 60℃, if the NaCl concentration is close to the solubility limit of 390 g / L and the calculated SI(NaCl)≈0.1-0.3, it indicates that the controlled crystallization region has been entered. If the solubility of Na2SO4 at this temperature is approximately 280 g / L, and the current concentration reaches more than 95% of its solubility, it may preferentially precipitate. By ranking the SI values ​​of the major salts, the crystallization priority order can be determined, for example: Na2SO4→NaCl→double salts. If the system still contains a small amount of CaSO4, its solubility is low, and it usually reaches supersaturation at a low concentration, which may serve as the initial nucleation species. To verify the judgment, a small-scale cooling crystallization experiment can be conducted, slowly cooling the concentrate from 60℃ to 40℃ (cooling rate 1-2℃ / min), observing the crystallization initiation temperature and crystal morphology, and observing the crystal structure and particle size distribution under a microscope.

[0040] After identifying the primary crystal type, select crystals of the same type or with similar structures as seed crystals to induce nucleation and control crystal growth. The seed crystal size should be controlled between 100-300 μm, providing sufficient nucleation surface area while minimizing carryover by the liquid flow. The seed crystal dosage is calculated as 3-8% of the concentrate mass; for example, for a single batch of 10 t concentrate, the seed crystal dosage would be 300-800 kg. Industrial-grade salt crystals with a purity ≥95% are typically selected as seed crystals and sieved to ensure uniform particle size distribution. Continuous quantitative addition is employed, using a screw feeder or metering conveyor to gradually add the crystals over 5-20 minutes to avoid sudden drops in local supersaturation or agglomeration caused by large-scale instantaneous addition. During addition, maintain moderate stirring (80-120 rpm) to ensure uniform seed crystal dispersion.

[0041] Based on the crystallization priority order and solubility variation law, the operating conditions of the crystallization unit are set. If the main crystallizer is Na2SO4, its solubility changes significantly with temperature, and crystallization can be induced by controlling the cooling gradient. Typically, the feed temperature is gradually reduced from 60℃ to 40℃, with the cooling rate controlled at 0.5-1℃ / min to form a stable temperature gradient. The circulation ratio is set to 15-30 times the evaporation rate; for example, if the evaporation rate is 1 t / h, the circulation flow rate is controlled at 15-30 t / h to enhance heat transfer and crystal suspension. The stirring intensity is controlled at 100-150 rpm to keep the crystals in suspension but avoid breakage. The entire crystallization process is maintained for 2-6 hours to allow sufficient crystal growth time. The slurry state is monitored using an online turbidity meter and particle size analyzer. When the average crystal particle size reaches 300-600 μm and the supersaturation index drops to near 0, it indicates that the crystallization process is stabilizing.

[0042] After seed crystal addition and operating parameter settings are completed, maintain the circulation rate, temperature gradient, and stirring intensity within the set range for 2-6 hours. Crystals gradually grow on the seed surface, and the supersaturation in the solution gradually decreases. Monitor solution concentration changes using a densitometer and conductivity meter to ensure a stable crystallization process. Typically, the concentrate density may increase from 1.25 g / cm³. 3 Decreased to 1.22 g / cm 3 The conductivity decreases by 5-10%, indicating that some solute has been converted into the solid phase. A crystalline slurry with a solid content of approximately 20-35% is formed, with crystal particle sizes concentrated in the range of 300-800 μm. The particles are regular in shape, facilitating subsequent centrifugation or pressure filtration. By controlling the seed crystal addition ratio (3-8%), continuous addition time (5-20 min), circulation ratio (15-30 times), and holding time (2-6 hours), a stable and controllable crystallization process can be achieved, improving crystal quality and separation efficiency.

[0043] In this embodiment, the specific steps of step S5 are as follows: The crystallized slurry is transported to a solid-liquid separation unit for separation processing to obtain solid salt and mother liquor; The solid salt is sent to a drying unit for drying to obtain the solid salt product. Component analysis is performed on solid salt products. If the solid salt product is detected to be a mixed salt or contains heavy metal salts, it shall be disposed of in accordance with the hazardous waste packaging regulations. The mother liquor is tested for particle concentration. When the particle concentration is lower than the preset threshold, it is determined to be harmless and qualified water. The harmless and qualified water is returned to the production system as recycled water, completing the zero-discharge treatment operation.

[0044] In this embodiment, after the crystallization stage, the crystallized slurry with a solid content of approximately 20-35% is transported to the solid-liquid separation unit via a corrosion-resistant slurry pump. The flow rate is controlled at 1-3 m / s during the transport process. 3 To avoid high-speed shearing damaging the crystal structure, a horizontal spiral sedimentation centrifuge or plate and frame filter press is typically used for solid-liquid separation. If centrifugation is used, the drum speed is controlled at 3000-4000 rpm, achieving a separation factor of 2000-3000 g, allowing crystals larger than 300 μm to settle rapidly. The feed concentration is controlled at around 25% to ensure a balance between separation efficiency and processing capacity. The water content of the solid phase after centrifugation can generally be reduced to 15-25%. If plate and frame filter press is used, the filtration pressure is set at 0.6-1.0 MPa, the single-cycle filtration time is 20-40 minutes, and the filter cake thickness is controlled at 20-40 mm. The water content after filtration can be controlled at around 20%. Two parts are obtained: a water-containing solid salt filter cake and a clarified mother liquor. The conductivity of the mother liquor is usually still in the range of 80-150 mS / cm, but the concentration of suspended particles is significantly reduced. During the separation process, the filtrate turbidity (target ≤100 NTU) and solid phase recovery rate (≥95%) need to be monitored regularly to ensure effective salt separation. The separated wet salt filter cake has a moisture content of approximately 20%, requiring further drying. The drying method employs a combination of low-temperature hot air and vacuum-assisted drying. The filter cake is evenly spread on a drying tray or placed in a rotary vacuum dryer, with a layer thickness controlled at 30-50 mm to ensure uniform heat transfer. The vacuum pump is started, and the pressure in the drying chamber is adjusted to -0.06 to -0.09 MPa. Under this negative pressure condition, the boiling point of water decreases, which is beneficial for low-temperature dehydration. The drying temperature is set in the range of 80-90℃, and the hot air circulation speed is controlled at 1.5-3.0 m / s to ensure uniform heat distribution. The drying time is determined based on the initial moisture content and the thickness of the packing, generally 2-4 hours. During the process, the moisture content change is measured using an online moisture analyzer or by periodic sampling and weighing. Drying is considered complete when the moisture content of the solid salt drops below 5%. Typically, the moisture content can be reduced from 20% to 3-4%. Low-temperature vacuum drying can prevent the salts from decomposing or agglomerating at high temperatures, maintaining the integrity of the crystal particles. After drying, a loose granular solid salt product is obtained, with the particle size maintained in the range of 300-800 μm.

[0045] X-ray diffraction analysis is used to determine the main crystal form and confirm whether it is a single salt (such as NaCl or Na2SO4) or a mixed salt structure. Subsequently, ICP-OES is used to detect the content of heavy metal elements, including Pb, Cd, Cr, Hg, and Ni, with detection limits typically below 0.01 mg / L. If the test results show a single harmless salt and the heavy metal content is below the relevant environmental standard limits, it can be managed as general industrial solid waste. If it is a mixed salt or the detected heavy metal content exceeds the limits (e.g., Pb > 5 mg / kg or Cr > 10 mg / kg), it must be packaged and disposed of according to hazardous waste management regulations. Specifically, it is packaged in leak-proof ton bags or sealed steel drums, labeled with hazardous waste labels, and the source, batch, and test data are recorded. It is then handed over to a qualified unit for harmless treatment or landfill. Through strict component analysis and classification management, it can be ensured that the disposal of solid salts complies with environmental regulations and avoids the risk of secondary pollution.

[0046] Turbidity is measured using an online turbidimeter, with a target value typically set at ≤50 NTU. Simultaneously, a laser particle size analyzer is used to detect the concentration and size distribution of suspended particles. The preset particle concentration threshold is usually ≤100 mg / L (or set according to reclaimed water requirements). If the test results show that the particle concentration is below the threshold and there are no obvious fine crystals suspended, the liquid can be considered qualified. If necessary, COD (target ≤50 mg / L) and conductivity (determined according to the reuse purpose) can be further tested to ensure that the mother liquor does not contain excessive contaminants. If the particle concentration exceeds the standard, microfiltration or re-sedimentation treatment is required to further reduce suspended solids. Once the mother liquor is confirmed to meet the particle concentration and water quality requirements, it is pumped back to the production process as reclaimed water, for example, for equipment cleaning, circulating cooling, or process makeup. The reuse flow rate is adjusted according to the production water demand, generally controlled within the range of 0.5-2 t / h. Before reuse, homogenization and buffering can be performed in storage tanks to avoid instantaneous water quality fluctuations affecting production. Throughout the process, water balance data is continuously recorded to ensure zero external discharge and achieve closed-loop circulation. Through full-process control of crystallization separation, low-temperature vacuum drying, standardized solid salt disposal, and mother liquor reuse, water and salt in high-salt / high-concentration waste liquids are recovered or safely disposed of, thereby achieving the goal of zero-discharge treatment.

[0047] In this embodiment, a high-efficiency treatment device for high-salt, high-concentration waste liquid using a low-temperature evaporation process is provided, for performing the high-efficiency treatment method for high-salt, high-concentration waste liquid using the low-temperature evaporation process described above, including: The water quality monitoring module is used to transport waste liquid to a storage tank, detect water quality parameters, and obtain a sediment assessment report. The softening and settling module is used to soften and settle the waste liquid based on the settling assessment report to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. The evaporation and concentration module is used to perform evaporation and concentration in the low-temperature evaporation unit to obtain a concentrated liquid and transport it to the crystallization unit. The crystallization module is used to perform crystallization processing in the crystallization unit to obtain a crystallized slurry. The evaluation module is used to perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; and return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

[0048] Therefore, the embodiments should be considered as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the application are intended to be included within the invention.

[0049] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein are implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for the efficient treatment of high-salt, high-concentration waste liquid using a low-temperature evaporation process, characterized in that, Includes the following steps: Step S1: The waste liquid is transported to a storage tank for water quality parameter testing to obtain a sediment assessment report; Step S2: Based on the precipitate assessment report, the waste liquid is softened and precipitated to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. Step S3: Evaporation and concentration are carried out in the low-temperature evaporation unit to obtain concentrated liquid, which is then transported to the crystallization unit; Step S4: Perform crystallization treatment in the crystallization unit to obtain crystallized slurry; Step S5: Perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation; The specific steps of step S1 are as follows: Waste liquid is transported to a storage tank via pipeline for continuous stirring and water quality parameter testing to extract waste liquid information, including conductivity, pH value, temperature, turbidity, COD, and calcium and magnesium ion concentration. Water quality characteristics are analyzed based on waste liquid information to generate a water quality characteristic matrix; Based on the water quality feature matrix, high-hardness scale-forming ions are identified to determine the types of precipitates. Calculate the supersaturation index and potential sediment amount of various precipitates based on waste liquid information; conduct water quality assessment based on precipitate type, supersaturation index, and potential sediment amount to obtain a precipitate assessment report; The specific steps of step S2 are as follows: Based on the precipitate assessment report, acid-base neutralization analysis was performed to determine the type of softening agent. Calculate the dosage based on the precipitate assessment report; Decision analysis is conducted based on the type and dosage of softening agent to obtain the dosing strategy; Based on the dosing strategy, the dosing metering pump set adds chemicals to the water storage tank for softening and sedimentation treatment; The precipitate is removed by the solid-liquid separation unit to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit.

2. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 1, characterized in that, Step S3 is as follows: Adjust the low-temperature evaporation unit to a negative pressure environment, set the evaporation temperature to the target range, start the evaporation and concentration program to evaporate and concentrate the pretreatment liquid, obtain the concentrate, and simultaneously detect the density and supersaturation of the concentrate. The concentration endpoint is set as the solubility limit of the waste liquid. The concentration endpoint is determined based on the concentration and supersaturation of the concentrate. When a concentration endpoint signal is detected in the current solution, the concentrate is transported to the crystallization unit.

3. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 2, characterized in that, During the evaporation and concentration process, the water vapor generated by the evaporation and concentration is detected; the water vapor is cooled by a condenser to obtain condensate; the conductivity and COD of the condensate are calculated; the conductivity and COD are tested for dual indicators, and when the test results meet the standards, the condensate is returned to the production system as recycled water. If the test results are not up to standard, activated carbon can be used for adsorption treatment.

4. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 3, characterized in that, The specific steps of step S4 are as follows: Calculate the conductivity and different ion concentrations of the concentrate to obtain the current solution state; Based on the current solution state, crystallization analysis is performed to determine the main crystal types and crystallization priority order; Seed crystals are screened according to the main crystallization type to obtain seed crystal information; the seed crystal information includes the seed crystal size range, dosage, and dosage type. Based on the crystallization priority order, the temperature gradient, circulation rate, and stirring intensity of the crystallization unit are set to obtain the control parameters; Based on the control parameters and seed crystal information, the crystallization unit is driven to perform crystallization treatment to obtain crystallization slurry.

5. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 4, characterized in that, The dosage is 3-8% of the concentrate mass, the seed crystal size range is 100-300μm, the seed crystal is added continuously and quantitatively, and the addition time is controlled as a gradual addition of 5-20 min; the circulation ratio is set to 15-30 times the evaporation rate; the addition treatment state is maintained for 2-6 hours.

6. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 1, characterized in that, The specific steps of step S5 are as follows: The crystallized slurry is transported to a solid-liquid separation unit for separation processing to obtain solid salt and mother liquor; The solid salt is sent to a drying unit for drying to obtain the solid salt product. Component analysis is performed on solid salt products. If the solid salt product is detected to be a mixed salt or contains heavy metal salts, it shall be disposed of in accordance with the hazardous waste packaging regulations. The mother liquor is tested for particle concentration. When the particle concentration is lower than the preset threshold, it is determined to be harmless and qualified water. The harmless and qualified water is returned to the production system as recycled water, completing the zero-discharge treatment operation.

7. The method for efficient treatment of high-salt, high-concentration waste liquid using the low-temperature evaporation process according to claim 6, characterized in that, The drying process specifically involves: low-temperature hot air drying; a drying temperature range of 80-90℃; a vacuum degree of -0.06 to -0.09 MPa; and a solid salt moisture content of less than 5%.

8. A high-efficiency treatment device for high-salt, high-concentration waste liquid using a low-temperature evaporation process, characterized in that, A method for efficiently treating high-salt, high-concentration waste liquid using the low-temperature evaporation process as described in claim 1, comprising: The water quality monitoring module is used to transport waste liquid to a storage tank, detect water quality parameters, and obtain a sediment assessment report. The softening and settling module is used to soften and settle the waste liquid based on the settling assessment report to obtain a pretreated liquid; the pretreated liquid is then transported to the low-temperature evaporation unit. The evaporation and concentration module is used to perform evaporation and concentration in the low-temperature evaporation unit to obtain a concentrated liquid and transport it to the crystallization unit. The crystallization module is used to perform crystallization processing in the crystallization unit to obtain a crystallized slurry. The evaluation module is used to perform solid-liquid separation treatment on the crystallized slurry to obtain solid salt and mother liquor; determine that the mother liquor is harmless and qualified water; and return the harmless and qualified water to the production system as recycled water to complete the zero-discharge treatment operation.

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