A seed-based MVR anti-scaling evaporation system and method

Abstract

This invention discloses a seed-based MVR anti-scaling evaporation system and method. The system includes an evaporator, a circulating pump, a separator, a scrubber, a steam compressor, and a seed crystal dosing unit. The evaporator has two layers of spiral groove distributors at its top for distributing the raw material liquid feed. The upper spiral groove is a pre-distribution layer, and the lower spiral groove is an adjustment layer. The lower and upper spiral grooves are staggered, with the pitch P1 of the upper spiral groove being greater than the pitch P2 of the lower spiral groove, and the depth H1 of the upper spiral groove being less than the depth H2 of the lower spiral groove. The seed crystals are surface-modified nano-SiO2 coated particles, with nano-SiO2 as the core and a functional layer formed on the core surface through chemical modification. Compared with traditional MVR devices, this invention extends the scaling cycle, reduces the cleaning frequency, and improves overall energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and more specifically, to a seed crystal method MVR anti-scaling evaporation system and method. Background Technology

[0002] Desulfurization wastewater, due to its weakly acidic nature and complex composition, presents a significant technical challenge in industrial wastewater treatment. This type of wastewater typically contains high concentrations of suspended solids, heavy metal ions, and corrosive substances such as chlorides (Cl- concentration reaching 5000-50000 ppm) and sulfates (SO42- concentration 2000-50000 ppm). Its chemical oxygen demand (COD) is primarily driven by inorganic reducing pollutants, leading to the failure of traditional biological treatment processes. Current mainstream concentration technologies have significant limitations. For example, although multi-effect flash evaporation achieves staged concentration through a three-stage evaporator, its reliance on external heat sources (steam / hot water) results in high operating costs, and the large footprint of the equipment cluster leads to high initial investment costs. While mechanical vapor recompression (MVR) technology achieves energy-saving breakthroughs through steam recycling (energy efficiency ratio of 1:15-1:20), during its evaporation and concentration process, impurities such as calcium sulfate and silica in the concentrated brine easily form crystal nuclei on the heat exchange surface. As the crystal nuclei continue to grow, they form a dense scale layer, causing the equipment's heat transfer efficiency to decrease by more than 30% and leading to the risk of flow channel blockage.

[0003] To address the aforementioned scaling problem, existing technologies generally employ regular cleaning and chemical prevention solutions. Regular cleaning can remove scale from the evaporator surface, but it increases downtime and maintenance costs. Chemical prevention can reduce scale formation by adding scale inhibitors, but it increases treatment costs and affects product quality. Summary of the Invention

[0004] Based on this, the main objective of the present invention is to provide a seed-based MVR anti-scaling evaporation system and method, which, compared with traditional MVR devices, extends the scaling cycle, reduces the cleaning frequency, and improves overall energy efficiency.

[0005] To achieve the above objectives, the present invention provides a seed-based MVR anti-scaling evaporation system, comprising:

[0006] An evaporator has a heat exchange surface and uses steam as a heat source to heat the raw liquid to evaporate it, thereby obtaining a concentrated liquid and secondary steam.

[0007] The circulating pump is connected to the inside of the evaporator to maintain the circulation of materials within the evaporator.

[0008] The separator, connected to the steam outlet of the evaporator, is used to remove liquid droplets entrained in the secondary steam.

[0009] The scrubber, connected to the steam outlet of the separator, is used to purify the steam;

[0010] A steam compressor, connected to the steam outlet of the scrubber and the steam inlet of the evaporator, is used to compress the purified steam from the scrubber and return it to the evaporator as a heat source;

[0011] The seed hydrocyclone is connected to the concentrated liquid outlet of the evaporator and is used to separate crystal particles from mother liquor in the concentrated liquid by hydrocyclone separation, so that the fine seed crystals enter the concentrated liquid tank and the coarse seed crystals are returned to the material inside the evaporator.

[0012] The seed crystal addition unit is connected to the evaporator and is used to add seed crystals into the evaporator.

[0013] The evaporator is equipped with two spiral groove distributors at the top for feeding and distributing raw material liquid. The upper spiral groove is a pre-distribution layer, and the lower spiral groove is an adjustment layer. The lower spiral groove is staggered with the upper spiral groove. The pitch P1 of the upper spiral groove is greater than the pitch P2 of the lower spiral groove, and the depth H1 of the upper spiral groove is less than the depth H2 of the lower spiral groove.

[0014] The seed crystal is a surface-modified nano-SiO2 coated particle, with nano-SiO2 as the core and a functional layer formed on the surface of the core through chemical modification.

[0015] Furthermore, the lower spiral groove and the upper spiral groove are misaligned as follows: the phase height difference between the lower and upper spirals is 50-100mm.

[0016] Furthermore, the seed crystal addition unit includes a seed crystal storage tank and a seed crystal pump, wherein the seed crystal pump pumps the seed crystals from the seed crystal storage tank and adds them into the evaporator.

[0017] Furthermore, the system also includes a preheater connected to the evaporator inlet, used to preheat the raw material liquid to a certain temperature before it enters the evaporator.

[0018] Furthermore, the system also includes a control unit and a crystal detection device, a thermal conductivity measuring device, and a solution density meter connected to the control unit.

[0019] Furthermore, the system also includes sensors connected to the control unit, including:

[0020] Temperature sensors are used to monitor evaporation temperature and secondary steam temperature;

[0021] Pressure sensors are used to monitor evaporator pressure and compressor inlet and outlet pressures;

[0022] Flow sensors are used to monitor feed flow and circulation flow.

[0023] pH sensor is used to detect the acidity or alkalinity of a solution;

[0024] A turbidity sensor is used to detect the concentration of suspended solids in a solution.

[0025] Furthermore, the system also includes a chemical dosing unit connected to the evaporator for adding scale inhibitors into the evaporator.

[0026] A second aspect of the present invention also provides a method for preventing scale evaporation in MVR using a seed crystal method, comprising the following steps:

[0027] The raw material liquid enters from the top of the evaporator and passes through two layers of spiral groove distributors, so that the liquid is evenly distributed in the radial direction. Steam is introduced as a heat source, and the raw material liquid is heated and evaporated in the evaporator in a film-like manner to obtain concentrated liquid and secondary steam.

[0028] The material is kept circulating within the evaporator by a circulating pump;

[0029] Secondary steam enters the separator to remove entrained liquid droplets, then enters the scrubber for washing to obtain purified steam; the purified steam enters the steam compressor for compression and returns to the evaporator as a heat source.

[0030] The concentrate enters the seed hydrocyclone to separate the crystal particles from the mother liquor by hydrocyclone separation, resulting in the fine seed crystals entering the concentrate tank and the coarse seed crystals returning to the evaporator.

[0031] In this process, seed crystals are added inside the evaporator. The seed crystals are surface-modified nano-SiO2 coated particles. The particles have nano-SiO2 as their core, and the surface of the core is chemically modified to form a functional layer.

[0032] Furthermore, the circulation pump has a circulation ratio of 20-50 times (i.e., the ratio of evaporation to circulation is 1:20-50), and the tube speed in the falling film evaporator is controlled at 2-2.5 m / s.

[0033] Furthermore, the particle size of the seed crystals ranges from 50 to 200 μm, and the seed crystal content in the evaporator is controlled at a mass ratio of 5 to 10%. The seed crystals are activated before being added to the evaporator: the seed crystals are placed in a seed activation box and prepared to a concentration of 8 to 10%, the stirrer is turned on for stirring, the seed crystal activation time is 600 to 1200 minutes, and the sedimentation ratio SV10 is 20 to 30%.

[0034] Furthermore, the method also includes: adding a scale inhibitor into the evaporator, preferably a dendritic macromolecular polymer or a dispersant scale inhibitor.

[0035] Furthermore, the method also includes: using the influent volume, solution density, and TDS (total dissolved solids) as reference data, adjusting the circulation pump frequency through a control unit.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention provides a seed-based MVR anti-scaling evaporation system and method, which innovates in three aspects: structure, materials, and control. It optimizes liquid distribution through a two-layer spiral grooved distributor (structural innovation), regulates nucleation by surface-modified nanocrystal seeds (material innovation), and implements multi-parameter intelligent control (control innovation), thereby achieving full-process anti-scaling from liquid distribution to crystal growth.

[0038] In addition, the present invention employs a synergistic effect of seed crystals and scale inhibitors. Surface-modified seed crystals reduce crystal deposition through directional adsorption, while scale inhibitors inhibit crystallization through dispersion. The combined use of the two can reduce the amount of scale inhibitor used by more than 30% while improving the utilization rate of seed crystals.

[0039] Furthermore, this invention achieves dynamic flushing through a high-flow-rate circulating pump, which, in conjunction with ultrasonic / scraper descaling, extends the cleaning cycle (≥30 days) and reduces downtime losses.

[0040] This invention is applicable to high-salinity wastewater (TDS > 50,000 mg / L), chemical evaporation (such as sodium sulfate and sodium chloride solutions), and food concentration (such as fruit juice and whey), achieving the following technical effects: the scaling cycle is extended to 3-5 times that of traditional processes; cleaning agent consumption is reduced by more than 50%; system thermal efficiency is increased to 90%-95% (compared to 80%-85% for traditional processes); and operating costs (energy consumption + chemicals) are reduced by 20%-30%.

[0041] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the seed-method MVR anti-scaling evaporation system provided in an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the spiral groove type distributor structure used in an embodiment of the present invention.

[0044] The attached diagram is labeled as follows: Steam compressor 1, Seed hydrocyclone 2, Evaporator 3 (falling film evaporator), Separator 4, Circulating pump 5, Scrubber 6, Preheater 7, Condenser 8, Deaerator 9, Raw water tank 10, Recycled water tank 11, Concentrate tank 12, Temperature sensor 13, Pressure sensor 14, Flow sensor 15, pH sensor 16, Densitometer 17, Differential pressure sensor 18, Conductivity meter 19, Turbidity meter 20, Chemical dosing unit (21-24), Cleaning unit 25, Scraper device 26, Ultrasonic descaling device 27, Magnetization treatment device 28, Vibrator 29, Online monitoring system 30, Alarm system 31, Safety interlock device 32, Control system 33, Pretreatment unit 34, Seed addition unit 35. Detailed Implementation

[0045] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0046] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of technical features indicated. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0047] In the description of this application, the term "comprising" and any variations thereof mean non-exclusive inclusion, meaning that one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added. Terms indicating orientation or positional relationships, such as "center," "lateral," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," are used to describe the orientation or relative positional relationships shown in the accompanying drawings and are merely for the purpose of simplifying the description of this application. They do not indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting this application.

[0048] Furthermore, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0049] like Figure 1 As shown, the present invention provides a seed crystal method MVR anti-scaling evaporation system, comprising:

[0050] An evaporator, having a heat exchange surface, uses steam as a heat source to heat wastewater to evaporate it, obtaining concentrated liquid and secondary steam;

[0051] The circulating pump is connected to the inside of the evaporator to maintain the circulation of materials within the evaporator.

[0052] The separator, connected to the steam outlet of the evaporator, is used to remove liquid droplets entrained in the secondary steam.

[0053] The scrubber, connected to the steam outlet of the separator, is used to purify the steam;

[0054] A steam compressor, connected to the steam outlet of the scrubber and the steam inlet of the evaporator, is used to compress the purified steam from the scrubber and return it to the evaporator as a heat source;

[0055] The seed hydrocyclone is connected to the concentrated liquid outlet of the evaporator and is used to separate crystal particles from mother liquor in the concentrated liquid by hydrocyclone separation, so that the fine seed crystals enter the concentrated liquid tank and the coarse seed crystals are returned to the material inside the evaporator.

[0056] The seed crystal addition unit is connected to the evaporator and is used to add seed crystals into the evaporator.

[0057] The evaporator is equipped with two spiral groove distributors at the top for wastewater feed distribution. The upper spiral groove is a pre-distribution layer, and the lower spiral groove is an adjustment layer. The lower spiral groove is staggered with the upper spiral groove. The pitch P1 of the upper spiral groove is greater than the pitch P2 of the lower spiral groove, and the depth H1 of the upper spiral groove is less than the depth H2 of the lower spiral groove.

[0058] The seed crystal is a surface-modified nano-SiO2 coated particle, with nano-SiO2 as the core and a functional layer formed on the surface of the core through chemical modification.

[0059] In some specific implementations, the evaporator adopts a falling film evaporation mode. The top of the evaporator is equipped with two layers of spiral groove type distributors, and a heat exchange tube is installed below the distributor. Steam is introduced through the outside of the heat exchange tube. The heat exchange tube is made of titanium alloy (Ti2) with a diameter of DN50, which has excellent corrosion resistance and thermal conductivity.

[0060] In this invention, a two-layer spiral grooved distributor is used to achieve double-layer flow guidance and graded uniformity.

[0061] The first (upper) spiral groove: its main function is pre-distribution, which initially guides the liquid from the top in a spiral flow, reduces the kinetic energy of the liquid directly impacting the top of the heat exchange tube, and avoids droplet splashing; at the same time, through spiral expansion, the liquid is initially homogenized in the radial direction.

[0062] The second (lower) spiral groove is offset from the first layer (e.g., a spiral phase height difference of 50-100mm). Its main function is to finely adjust and guide the liquid after the first layer is pre-distributed in a secondary spiral, further eliminating radial non-uniformity and ensuring that the liquid contacts the heat exchange tube surface in a more stable spiral path, forming a liquid film with a more uniform thickness.

[0063] In addition, the distributor is designed to dynamically match flow rate and viscosity:

[0064] The pitch, depth, and width of the two-layer grooves can be designed independently (e.g., the upper layer has a large pitch and the lower layer has a small pitch). The upper layer reduces the liquid kinetic energy by using a "large pitch + shallow groove" and the lower layer enhances the flow stability by using a "small pitch + deep groove". This allows for adaptability to different flow rates (e.g., the lower groove is deepened at low flow rates to maintain liquid film continuity, and the upper groove is widened at high flow rates to disperse the flow) and different viscosities of liquids (e.g., a deeper lower groove is needed for high-viscosity liquids to reduce flow resistance).

[0065] The inter-level liquid redistribution of this distributor can also achieve anti-clogging and self-cleaning:

[0066] If the liquid contains a small amount of solid particles, the first layer of grooves can trap larger particles (through the design of the groove width), and the second layer of grooves performs secondary filtration and redistribution of the liquid through a denser spiral path, preventing particles from accumulating at the top of the heat exchange tubes; at the same time, the staggered arrangement of the two layers of grooves can create a "shear effect", reducing dead zones during liquid flow and lowering the risk of scaling.

[0067] In some specific implementations, the parameters of the two trenches (pitch P1, depth H1, width W1; pitch P2, depth H2, width W2) are independently adjustable to adapt to feed solutions of different viscosities and flow rates.

[0068] In some specific implementations, the seed crystal addition unit includes a seed crystal storage tank and a seed crystal pump, wherein the seed crystal pump pumps the seed crystals from the seed crystal storage tank and adds them into the evaporator.

[0069] In this invention, the seed crystals used have nano-SiO2 as their core (possessing high mechanical strength and chemical stability), and their surfaces are modified to form functional layers (such as hydrophilicity / hydrophobicity adjustment and charge modification) to enhance their interaction with target ions in solution. Furthermore, controllable hydrophilicity / hydrophobicity can be achieved: surface modification can adjust the hydrophilicity of the particles (e.g., by introducing hydrophilic groups such as -OH and -COOH) or hydrophobicity (e.g., by introducing -CH3 or fluorinated groups) to match the wetting requirements of different solution systems (e.g., high-salt wastewater, organic solutions), reducing particle agglomeration. Surface charge regulation can also be achieved: by introducing positive charges (e.g., amino modification) or negative charges (e.g., carboxyl modification), electrostatic adsorption with oppositely charged ions in solution is enhanced, promoting the directional alignment of ions on the particle surface and accelerating nucleation.

[0070] Furthermore, while nanoparticles are prone to agglomeration, surface modification (such as polymer grafting or small molecule modification) can introduce steric hindrance or electrostatic repulsion effects, significantly improving dispersibility (uniform suspension in solution) and avoiding scaling or uneven crystal size caused by localized supersaturation. The modified particles also exhibit improved thermal stability (e.g., through cross-linking and curing of the surface layer), maintaining structural stability under high-temperature evaporation conditions and extending the lifespan of the seed crystals.

[0071] In some specific implementation schemes, surface modification can be performed using silane coupling agents: modification with silane coupling agents such as KH-550 (introducing -NH2 groups, hydrophilic and positively charged) or KH-570 (introducing double bonds, suitable for polymer grafting) enhances the resistance to Ca in solution. 2+ SO4 2- The adsorption capacity of plasma can guide the nucleation of crystals in a specific direction.

[0072] Silane coupling agents (such as KH570) hydrolyze to generate silanol groups (-SiOH), which dehydrate and condense with hydroxyl groups on the SiO2 surface to form Si-O-Si covalent bonds, while simultaneously introducing organic functional groups (such as methacryloxy groups). For example, the specific process includes: dispersing nano-SiO2 in an ethanol-water mixed solution (volume ratio 3:1), adding 1%-5% silane coupling agent, and refluxing at 60-80°C for 2-4 hours. The absolute value of the product's Zeta potential can reach over 40mV, and the dispersion stability is improved by 5 times.

[0073] In some specific implementations, the seed crystals can be controlled in terms of particle size and concentration, and the seed crystals can be activated before being added to the evaporator: for example, the particle size range of the seed crystals is 50-200μm, the seed crystals are placed in a seed activation box and prepared to a concentration of 8-10%, the stirrer is turned on to stir, ensuring that the seed crystals are uniformly suspended in the solution, the seed crystal activation time is 600-1200 minutes, the sedimentation ratio SV10 is 20-30%, and the seed crystal content in the evaporator is controlled to be 5-10% by mass.

[0074] In some specific implementation schemes, the concentrate is pumped to the hydrocyclone via a seed hydrocyclone pump. The overflow from the hydrocyclone (containing fine seed crystals) enters the concentrate tank, while the underflow (containing coarse seed crystals) returns to the inlet pipe of the circulation pump. This achieves the recycling of seed crystals and particle size classification control, avoiding the deposition risk caused by excessive seed crystal growth.

[0075] In some specific embodiments, the system further includes a chemical dosing unit connected to the evaporator for adding scale inhibitors into the evaporator. When selecting a scale inhibitor, simulated evaporation experiments can be conducted, including selecting a suitable scale inhibitor and dosage based on the properties of the wastewater and the operating conditions of the evaporator, such as dendritic macromolecular polymers or dispersant scale inhibitors.

[0076] In this invention, scale inhibitors and seed crystals can achieve synergy: depending on the properties of the wastewater (e.g., Ca... 2+ SO4 2- The molar ratio and organic matter content, along with operating conditions (evaporation temperature and flow rate), are used to determine the matching relationship between scale inhibitor type (such as polycarboxylic acid and phosphate) and seed crystal surface modification scheme through simulated evaporation experiments, and optimize the dosage (scale inhibitor: 5-20 mg / L based on water volume; seed crystal: 10-20%, based on water mass).

[0077] In some specific embodiments, the chemical dosing unit also includes adding other agents such as defoamers, cleaning agents, acids, and calcium chloride into the evaporator.

[0078] In some specific embodiments, the system also includes a preheater connected to the evaporator inlet, used to preheat the raw material liquid to a certain temperature (50℃-70℃) before it enters the evaporator, that is, to increase the feed temperature and reduce the energy consumption of subsequent evaporation.

[0079] In some specific embodiments, the system further includes a control unit and a crystal detection device, a thermal conductivity measuring device, and a solution density meter connected to the control unit.

[0080] In some specific implementations, the seed crystal content in the evaporator is controlled at 10-20%, and is detected online by a crystal detection device. This device consists of a densitometer, a hardness tester, and a chromatograph, and can obtain the seed crystal content instantaneously. When the seed crystal content is below 8%, the seed crystal addition unit replenishes the seed crystals; when the seed crystal content is above 20%, it can be discharged by a circulating pump. The detection accuracy of the crystal detection device is ±1%, and the response time is <30 seconds. Instantaneous data feedback provides control basis for the seed crystal addition unit.

[0081] In some specific implementations, the evaporator and preheater are equipped with thermal conductivity measuring devices (heat flow meters or infrared thermal imagers) that can monitor changes in thermal conductivity online. For example, when the thermal conductivity decreases (>5%), the system determines that there is a tendency to scale and triggers descaling intervention. At the same time, the thermal conductivity data is correlated with temperature, pressure and flow parameters to construct a dynamic scaling model and quantify the degree of scaling (such as scale thickness and increase in thermal resistance).

[0082] In some specific embodiments, the evaporator and preheater are equipped with an ultrasonic descaling device linked to a thermal conductivity measuring device. When the thermal conductivity decreases, for example, below 1200 W / (m²), the device will detect the scale buildup. 2 When the thermal conductivity is below the extreme threshold (e.g., 80% of the initial value), the ultrasonic descaling device (frequency adjustable to 20-40kHz, power 500-1000W) should be activated first to enhance the descaling capacity; if the thermal conductivity continues to be below the extreme threshold (e.g., 80% of the initial value), the scraper device (preheater section) should be activated or the cleaning process should be triggered.

[0083] In some specific embodiments, the system further includes sensors connected to the control unit, including but not limited to:

[0084] Temperature sensors are used to monitor evaporation temperature and secondary steam temperature;

[0085] Pressure sensors are used to monitor evaporator pressure and compressor inlet and outlet pressures;

[0086] Flow sensors are used to monitor feed flow and circulation flow.

[0087] pH sensor is used to detect the acidity or alkalinity of a solution;

[0088] A turbidity sensor is used to detect the concentration of suspended solids in a solution.

[0089] In this invention, the control unit can perform comprehensive analysis based on parameters such as thermal conductivity measurement device, flow rate, conductivity, turbidity, temperature, and pressure to achieve intelligent control. It can optimize the operation mode by adjusting the circulation pump frequency, scale inhibitor dosage, and seed crystal dosage. It also includes recording and analyzing anti-scaling effect data to evaluate the performance of the seed crystal dosing system and the online monitoring system and optimize the control operating parameters.

[0090] In some specific embodiments, the system further includes a cleaning unit connected to the evaporator and the preheater. The cleaning unit includes a cleaning tank and a cleaning pump. The cleaning agent is added to the evaporator and the preheater through the cleaning pump, and discharged after circulating and soaking.

[0091] In this invention, the cleaning unit analyzes the cleaning agent based on signals from the control unit, including the degree of scaling, the time of scaling, and the type of scaling, and then starts cleaning. After cleaning, the MVR can be restarted when the thermal conductivity recovers to 98%, according to the control unit's judgment. If the thermal conductivity is lower than 98%, the cleaning agent is replaced and cleaning is performed again.

[0092] A second aspect of the present invention also provides a method for preventing scale evaporation in MVR using a seed crystal method, comprising the following steps:

[0093] Wastewater enters from the top of the evaporator and passes through two layers of spiral groove distributors, so that the wastewater is evenly distributed radially. Steam is introduced as a heat source, and the wastewater is heated and evaporated in the evaporator in a film-like manner to obtain concentrated liquid and secondary steam.

[0094] The material is kept circulating within the evaporator by a circulating pump;

[0095] Secondary steam enters the separator to remove entrained liquid droplets, then enters the scrubber for washing to obtain purified steam; the purified steam enters the steam compressor for compression and returns to the evaporator as a heat source.

[0096] The concentrate enters the seed hydrocyclone to separate the crystal particles from the mother liquor by hydrocyclone separation, resulting in the fine seed crystals entering the concentrate tank and the coarse seed crystals returning to the evaporator.

[0097] In this process, seed crystals are added inside the evaporator. The seed crystals are surface-modified nano-SiO2 coated particles. The particles have nano-SiO2 as their core, and the surface of the core is chemically modified to form a functional layer.

[0098] In some specific implementations, the method further includes adding a scale inhibitor into the evaporator.

[0099] In some specific implementation schemes, the circulation pump has a circulation ratio of 20-50 times (i.e., the ratio of evaporation to circulation is 1:20-50), and the liquid film flow rate in the heat exchange tube during falling film evaporation is controlled at 2.0-2.5 m / s.

[0100] In some specific implementations, the method further includes adjusting the circulation pump frequency via a control unit, using the influent volume, solution density, and TDS (total dissolved solids) as reference data.

[0101] In this invention, the circulation pump frequency is interlocked with the influent flow rate, solution density (monitored by a densitometer), and TDS (total dissolved solids, monitored by a conductivity meter).

[0102] When the influent flow rate increases or the solution density / TDS increases, the circulation pump frequency automatically increases to improve the flow rate inside the tube, enhance the scouring effect of the liquid film on the heat exchange tube wall, and inhibit crystal deposition.

[0103] By using logic control algorithms (such as PID control), the flow rate inside the pipe is kept stable, avoiding scaling caused by excessively low flow rates or increased energy consumption caused by excessively high flow rates.

[0104] In some specific implementation schemes, to prevent scaling and corrosion, the pH inside the evaporator is strictly controlled with an accuracy of 7 ± 0.2.

[0105] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0106] Example 1

[0107] like Figure 1 As shown, a seed-based MVR anti-scaling evaporation system includes:

[0108] The system includes a steam compressor, seed cyclone separator, evaporator (falling film evaporator), separator, circulating pump, scrubber, preheater, condenser, deaerator, raw water tank, recycled water tank, concentrate tank, temperature sensor, crystal detection device, pressure sensor, flow sensor, pH sensor, density meter, differential pressure sensor, turbidity meter, conductivity meter, chemical dosing unit, seed crystal addition unit, cleaning unit, thermal conductivity measuring device, online monitoring system, alarm system, and control system. The functions of each device are as follows:

[0109] Steam compressor: The core equipment of the MVR system, which increases the temperature and pressure of the secondary steam generated by evaporation by compressing it, so that it can be used as a heat source again for heating, thus realizing the recycling of energy.

[0110] Seed hydrocyclone: ​​At the end of evaporation and crystallization, the crystal particles in the suspension are separated from the mother liquor by hydrocyclone, thereby increasing the crystal concentration; achieving the classification of coarse and fine crystals and optimizing the crystallization quality.

[0111] Evaporator: The main place for material evaporation, including heater, separator, circulating pump, etc.; it heats the material to make it evaporate, and the generated secondary steam is compressed by the compressor and reused.

[0112] Separator: A vapor-liquid separation device that separates the vapor produced by evaporation from the liquid, and the pure secondary vapor is sent to the compressor for recompression.

[0113] Circulation pump: Maintains the circulation of materials within the evaporator, increases flow rate to prevent scaling on heat exchange tubes; reduces the probability of local nucleation and promotes crystal growth.

[0114] Scrubber: Cleans impurities / harmful substances from steam or materials, ensuring clean system operation.

[0115] Preheater: Increases feed temperature and reduces subsequent evaporation energy consumption.

[0116] Condenser: It condenses the high-temperature, high-pressure steam compressed by the compressor into water and recovers latent heat; the resulting treated water can be reused.

[0117] Degasser: Removes non-condensable gases (such as air and CO2) from the system to maintain system vacuum and evaporation efficiency.

[0118] Raw water tank: Stores wastewater to provide a stable feed for the system.

[0119] Recycled water tank: Stores condensate generated by the system for reuse or further treatment.

[0120] Concentrate tank: Stores the concentrated liquid after evaporation and crystallization, which is convenient for subsequent processing or resource utilization.

[0121] A crystal detection device is used to detect the content of crystal seeds online.

[0122] A thermal conductivity measuring device that can detect thermal conductivity online.

[0123] Temperature sensor: Monitors the temperature of materials and secondary steam inside the evaporator, providing a basis for the control system to adjust.

[0124] Pressure sensor: Monitors the pressure inside the evaporator, the inlet and outlet pressures of the compressor, etc., to ensure that the system operates within a safe pressure range.

[0125] Flow sensor: monitors feed flow, discharge flow, circulation flow, etc., to guide material balance and flow regulation.

[0126] pH sensor: Monitors the pH value of materials to guide the dosage of scale inhibitors and defoamers, preventing scaling and foaming.

[0127] Densitometer: Monitors material density, guides material discharge and concentrate treatment, and ensures product quality.

[0128] Differential pressure sensor: monitors pressure drop in filters / heat exchangers, indicates blockage, and guides cleaning and maintenance.

[0129] Conductivity meter: monitors the conductivity of materials, reflects ion concentration, and guides the addition of scale inhibitors and defoamers.

[0130] Turbidity sensor (turbidity meter): Monitors the turbidity of materials, reflects the content of suspended solids, and guides filtration and cleaning operations.

[0131] Scale inhibitor dosing device: Adds scale inhibitor to prevent scale formation on the heat exchange surface and improve heat exchange efficiency.

[0132] Defoamer dosing device: Adds defoamer to eliminate evaporating foam and prevent it from affecting efficiency and product quality.

[0133] Calcium chloride dosing device: to adjust the ion concentration of the material or to act as a seed crystal to promote the crystallization process.

[0134] Acid dosing device: Adjusts the pH value of materials to prevent scaling and corrosion; may also be used to promote chemical reactions.

[0135] Cleaning unit: Regularly cleans equipment such as evaporators and heat exchangers to remove scale and impurities, and maintains heat exchange efficiency and operational stability.

[0136] Online monitoring system: Real-time monitoring of parameters such as temperature, pressure, flow rate, pH, density, conductivity, and turbidity, providing a basis for control system adjustment.

[0137] Alarm system: When system parameters exceed limits, an alarm signal is issued to remind operators to handle the situation promptly.

[0138] Safety interlock device: When the system malfunctions, it automatically interlocks and shuts down or takes safety measures to prevent the accident from escalating.

[0139] Control system: Based on online monitoring data and preset logic, it automatically adjusts the steam compressor speed, feed flow rate, discharge valve opening, etc., to ensure stable, efficient and safe operation of the system.

[0140] Based on the above functional description and the following method flow, those skilled in the art can easily obtain the physical connection relationship, material flow, inlet and outlet positions, communication relationship or other connection structure (e.g., valves, pumps, etc.) of each device. These will not be described in detail here, but can be referred to in the prior art.

[0141] The top of the evaporator is provided with two layers of spiral groove type distributors (such as...). Figure 2 As shown), it is used for wastewater feed distribution. The upper spiral groove is a pre-distribution layer, and the lower spiral groove is an adjustment layer. The lower spiral groove and the upper spiral groove are staggered. The pitch P1 of the upper spiral groove is greater than the pitch P2 of the lower spiral groove, and the depth H1 of the upper spiral groove is less than the depth H2 of the lower spiral groove.

[0142] In this embodiment, P1, H1, W1; P2, H2, W2 are 8mm, 40mm, 500mm; 6mm, 80mm, 800mm respectively, and the spiral phase height difference between the second spiral groove and the first spiral groove is 50-100mm.

[0143] The secondary steam generated by evaporation is pressurized and heated by a steam compressor and then returned to the heat exchange tubes of the evaporator as a heat source to achieve energy recycling; the condensate recovers heat through the condenser, and the uncondensed steam enters the degasser for treatment to ensure that the system thermal efficiency is >95%.

[0144] based on Figure 1 The method for preventing scale evaporation of the device shown includes the following steps:

[0145] Wastewater enters from the top of the evaporator and passes through two layers of spiral groove distributors, so that the wastewater is evenly distributed radially. Steam is introduced as a heat source, and the wastewater is heated and evaporated in the evaporator in a film-like manner to obtain concentrated liquid and secondary steam.

[0146] The material is kept circulating in the evaporator by a circulating pump with a circulation ratio of 50 times (i.e., the ratio of evaporation to circulation is 1:50). The liquid film flow rate in the heat exchange tube during falling film evaporation is controlled at 2.0-2.5 m / s.

[0147] Secondary steam enters the separator to remove entrained liquid droplets, then enters the scrubber for washing to obtain purified steam; the purified steam enters the steam compressor for compression and returns to the evaporator as a heat source.

[0148] The concentrate is pumped to the hydrocyclone via a seed hydrocyclone pump. The overflow from the hydrocyclone (containing fine seed crystals) enters the concentrate tank, while the underflow (containing coarse seed crystals) returns to the inlet pipe of the circulation pump. This achieves the recycling of seed crystals and particle size classification control, avoiding the deposition risk caused by excessive seed crystal growth.

[0149] The seed crystal is a surface-modified nano-SiO2 coated particle, wherein the particle has a nano-SiO2 core and a functional layer is formed on the surface of the core through chemical modification. The preparation process of the seed crystal is as follows: nano-SiO2 is dispersed in an ethanol-water mixed solution (volume ratio 3:1), 3% silane coupling agent KH570 is added, and the mixture is refluxed at 70°C for 3 hours to obtain the seed crystal.

[0150] Seed crystals are added to the evaporator circulation pipeline via a seed pump (the addition point is located before the circulation pump inlet), and the addition amount is controlled online by a crystal detection device. When the seed crystal content (mass fraction) is lower than 8%, the seed crystal addition system is automatically triggered to replenish the seed crystals.

[0151] The method also includes adding a scale inhibitor into the evaporator. The scale inhibitor is an acrylic copolymer and the dosage is 10 mg / L.

[0152] The method also includes controlling the pH inside the evaporator with an accuracy of 7 ± 0.2.

[0153] The method uses a thermal conductivity measuring device to monitor changes in thermal conductivity online. When the thermal conductivity decreases (>5%), the system determines that there is a tendency for scaling and triggers descaling intervention. At the same time, the thermal conductivity data is correlated with temperature, pressure, and flow parameters to construct a dynamic scaling model and quantify the degree of scaling (such as scale thickness and increase in thermal resistance).

[0154] The evaporator and preheater are equipped with an ultrasonic descaling device linked to a thermal conductivity measuring device. When the thermal conductivity measuring device drops below 1200 W / (m²), the device will detect the scale buildup. 2 ·K), the ultrasonic descaling device increases the frequency to 40Hz to enhance its descaling ability.

[0155] The preheater is equipped with a scraper device, which measures 1000 W / (m²) when the thermal conductivity measurement device reading is below the extreme value. 2 ·K), use a scraper to remove scale.

[0156] The method also includes a cleaning process: when the thermal conductivity measurement device value is consistently below 90% of the initial value, or the scale thickness exceeds 2mm (calculated by back-calculation using the thermal conductivity model), the control system automatically analyzes the type (inorganic salt scale, organic scale, or mixed scale) and degree of scale, and selects an appropriate cleaning agent (such as an acidic cleaning agent for carbonate scale and a chelating agent for sulfate scale).

[0157] The cleaning agent is added to the evaporator and preheater through a cleaning pump and discharged after 1-4 hours of circulating soaking. After cleaning, the system automatically detects the recovery of thermal conductivity. If the thermal conductivity recovers to more than 98%, the MVR system is restarted. If it does not meet the standard, the cleaning agent is replaced and the cleaning is repeated until the thermal conductivity meets the standard.

[0158] This embodiment of the treatment of high-salinity wastewater (TDS > 50,000 mg / L) achieves the following: the scaling cycle is extended to 5 times that of traditional processes; cleaning agent consumption is reduced by more than 50%; system thermal efficiency is increased to 95% (compared to 80%-85% for traditional processes); and operating costs (energy consumption + chemicals) are reduced by 25%.

[0159] Comparative Example 1

[0160] The difference from Example 1 is that a single-layer spiral grooved distributor is used, with parameters P, H, and W of 40mm, 6mm, and 5mm, respectively.

[0161] Compared with Example 1, in Comparative Example 1, after the liquid enters the trench from the top, it directly contacts the heat exchange tube through only one spiral flow. Fluctuations in the feed flow rate or improper design of the trench parameters lead to uneven liquid film thickness (such as thin at the edges and thick in the middle). It is less adaptable to high-viscosity liquids or liquids containing a small amount of solid particles, and is prone to trench blockage or liquid film breakage.

[0162] Comparative Example 2

[0163] The difference from Example 1 is that conventional seed crystals are used, specifically anhydrous CaSO4, and the seed crystal mass ratio is controlled at 5%.

[0164] In the treatment of desulfurization wastewater using the seed crystal method MVR, Example 1 of this invention uses surface-modified nano-SiO2 seeds, which, compared to Comparative Example 2 using conventional anhydrous CaSO4 seeds at a mass ratio of 5%, exhibits significant advantages in scale inhibition efficiency, nucleation kinetics, anti-agglomeration properties, and adaptability. The specific differences are as follows:

[0165] 1. Scale inhibition efficiency: Multi-target inhibition vs. single-target selectivity

[0166] Conventional CaSO4 seed crystals inhibit CaSO4 scale formation solely by providing heterogeneous nucleation sites; they have no direct inhibitory effect on scale types such as CaCO3 and SiO2. Experiments show that at a 5% mass ratio, their scale inhibition rate for CaSO4 scale is approximately 92%, but the overall scale inhibition rate (including other scale types) is less than 75%.

[0167] Surface-modified nano-SiO2 seeds: These seeds are negatively charged through surface carboxyl group (-COOH) modification, enabling them to simultaneously electrostatically adsorb Ca. 2+ Mg 2+ and SiO3 2- Plasma forms a dynamic ion-shielding layer, inhibiting the crystallization of various scale types. For example, under the same operating conditions, the overall scale inhibition rate is increased to 98%, and the inhibition rate of SiO2 scale is increased from 30% for conventional seed crystals to 85%.

[0168] 2. Nucleation kinetics: Nanoscale acceleration vs. micrometer-scale delay

[0169] Conventional CaSO4 seed crystals: micron-sized particles (1-10 μm) result in low specific surface area (<10 m²). 2 The nucleation induction period is relatively long (>30 minutes), and high concentration (5%) is required to maintain the effect.

[0170] Surface-modified nano-SiO2 seeds: Nanoscale cores (50-100nm) provide ultra-high specific surface area (200-300m²). 2 / g), with a surface silanol (-Si-OH) density of 10. 15 sites / cm 2 The nucleation induction period is shortened to within 5 minutes. Furthermore, the negatively charged surface (ζ potential = -35mV) attracts Ca through electrostatic attraction. 2+ This further reduces the nucleation energy barrier (ΔG* is reduced by 40%), achieving "low concentration and high efficiency" (1% mass ratio can achieve the effect of conventional 5%).

[0171] 3. Anti-agglomeration: Functional layer stability vs. physical dispersion dependency

[0172] Conventional CaSO4 seed crystals: In high-salt environments (NaCl > 5%), the electric double layer on the particle surface is compressed, and van der Waals forces dominate agglomeration, resulting in a wider particle size distribution (D50 increases from 5 μm to 20 μm) and a reduction of more than 30% in effective nucleation sites. Additional dispersants (such as sodium hexametaphosphate) are needed to maintain stability, but this may introduce secondary contamination.

[0173] Surface-modified nano-SiO2 seed crystals: By grafting polyethylene glycol (PEG) to form a steric hindrance layer, the interparticle spacing is maintained at >50nm, reducing the risk of hard agglomeration by 80%; at the same time, the controllable hydrophilic / hydrophobic design (such as fluorinated group modification) can match the wetting requirements of different solutions, and it still maintains a monodisperse state (D50<120nm) in 10% NaCl solution, ensuring long-term stability.

[0174] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A seed crystal method MVR anti-scaling evaporation system, characterized in that, include: An evaporator has a heat exchange surface and uses steam as a heat source to heat the raw liquid to evaporate it, thereby obtaining a concentrated liquid and secondary steam. The circulating pump is connected to the inside of the evaporator to maintain the circulation of materials within the evaporator. The separator, connected to the steam outlet of the evaporator, is used to remove liquid droplets entrained in the secondary steam. The scrubber, connected to the steam outlet of the separator, is used to purify the steam; A steam compressor, connected to the steam outlet of the scrubber and the steam inlet of the evaporator, is used to compress the purified steam from the scrubber and return it to the evaporator as a heat source; The seed hydrocyclone is connected to the concentrated liquid outlet of the evaporator and is used to separate crystal particles from mother liquor in the concentrated liquid by hydrocyclone separation, so that the fine seed crystals enter the concentrated liquid tank and the coarse seed crystals are returned to the material inside the evaporator. The seed crystal addition unit is connected to the evaporator and is used to add seed crystals into the evaporator. The evaporator is equipped with two spiral groove distributors at the top for feeding and distributing raw material liquid. The upper spiral groove is a pre-distribution layer, and the lower spiral groove is an adjustment layer. The lower spiral groove is staggered with the upper spiral groove. The pitch P1 of the upper spiral groove is greater than the pitch P2 of the lower spiral groove, and the depth H1 of the upper spiral groove is less than the depth H2 of the lower spiral groove. The seed crystal is a surface-modified nano-SiO2 coated particle, the particle having nano-SiO2 as its core, and the core surface forming a functional layer through chemical modification; the chemical modification is one of hydrophilicity adjustment, hydrophobicity adjustment, charge modification, grafting polymer or small molecule modification.

2. The seed-method MVR anti-scaling evaporation system according to claim 1, characterized in that, The lower spiral groove and the upper spiral groove are misaligned as follows: the phase height difference between the lower and upper spirals is 50-100mm.

3. The seed-method MVR anti-scaling evaporation system according to claim 1, characterized in that, The seed crystal addition unit includes a seed crystal storage tank and a seed crystal pump, wherein the seed crystal pump pumps the seed crystals from the seed crystal storage tank and adds them into the evaporator; and / or, The system also includes a preheater connected to the evaporator inlet, used to preheat the raw material liquid to a certain temperature before it enters the evaporator.

4. The seed-method MVR anti-scaling evaporation system according to claim 1, characterized in that, The system also includes a control unit and a crystal detection device, a thermal conductivity measuring device, and a solution density meter connected to the control unit; The system also includes sensors connected to the control unit, including: Temperature sensors are used to monitor evaporation temperature and secondary steam temperature; Pressure sensors are used to monitor evaporator pressure and compressor inlet and outlet pressures; Flow sensors are used to monitor feed flow and circulation flow. pH sensor is used to detect the acidity or alkalinity of a solution; A turbidity sensor is used to detect the concentration of suspended solids in a solution.

5. The seed-method MVR anti-scaling evaporation system according to claim 1, characterized in that, The system also includes a chemical dosing unit connected to the evaporator for adding scale inhibitors, defoamers, cleaning agents, calcium chloride, or acids into the evaporator.

6. A seed-based MVR method for preventing scaling and evaporation, employing the system described in any one of claims 1-5, characterized in that, Includes the following steps: The raw material liquid enters from the top of the evaporator and passes through two layers of spiral groove distributors, so that the liquid is evenly distributed in the radial direction. Steam is introduced as a heat source, and the raw material liquid is heated and evaporated in the evaporator in a film-like manner to obtain concentrated liquid and secondary steam. The material is kept circulating within the evaporator by a circulating pump; Secondary steam enters the separator to remove entrained liquid droplets, then enters the scrubber for washing to obtain purified steam; the purified steam enters the steam compressor for compression and returns to the evaporator as a heat source. The concentrate enters the seed hydrocyclone to separate the crystal particles from the mother liquor by hydrocyclone separation, resulting in the fine seed crystals entering the concentrate tank and the coarse seed crystals returning to the evaporator. In this process, seed crystals are added inside the evaporator. The seed crystals are surface-modified nano-SiO2 coated particles. The particles have nano-SiO2 as their core, and the surface of the core is chemically modified to form a functional layer.

7. The seed-method MVR anti-scaling and evaporation method according to claim 6, characterized in that, The circulation pump has a circulation ratio of 20 to 50 times, and the tube speed in the falling film evaporator is controlled at 2 to 2.5 m / s.

8. The seed-method MVR anti-scaling and evaporation method according to claim 6, characterized in that, The seed crystals have a particle size range of 50-200 μm, and the mass of the seed crystals in the evaporator accounts for 5-10% of the mass of the incoming water. The seed crystals are activated before being added to the evaporator: the seed crystals are placed in a seed activation box, prepared to a concentration of 8-10%, and stirred with a stirrer for 600-1200 minutes, with a settling ratio SV. 10 It is 20-30%.

9. The seed-method MVR anti-scaling and evaporation method according to claim 6, characterized in that, The method also includes adding a scale inhibitor into the evaporator.

10. The seed-method MVR anti-scaling and evaporation method according to claim 6, characterized in that, The method further includes using the influent volume, concentrate density, and total dissolved solids as reference data to adjust the circulation pump frequency through a control unit.

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