A multi-disc water film type concentrator and a low-temperature high-salinity wastewater evaporation concentration method thereof

Abstract

The present application relates to the technical field of high-salinity wastewater treatment, and discloses a multi-disc water film type concentrator and a low-temperature high-salinity wastewater evaporation and concentration method thereof, which comprises a shell and a disc assembly, a liquid storage tank is arranged in the shell, a liquid inlet is arranged on the shell, the disc assembly is rotationally arranged in the shell through a central shaft, an air inlet and an air outlet are arranged on the shell, the disc assembly comprises a plurality of discs arranged in parallel and stacked, disc gaps are formed between adjacent discs, turning flow channels are formed between the discs and the inner cavity of the shell, half of the discs are immersed in the wastewater in the liquid storage tank, the disc gaps above the liquid surface and the turning flow channels form a serpentine channel, and disc brushes are arranged in the disc gaps. The present application can efficiently and low-temperature evaporate and concentrate ultra-high-salinity wastewater to a level close to saturation, effectively avoids the scaling and pollution of the evaporation surface, and ensures the water film integrity and promotes the water film evaporation through the optimization of the flow channel design, material selection and disc surface modification, so as to realize the maximum energy efficiency of low-temperature evaporation.

Description

Technical Field

[0001] This invention relates to the field of high-salinity wastewater treatment technology, and more specifically to a multi-plate water film concentrator and a method for evaporating and concentrating low-temperature high-salinity wastewater. Background Technology

[0002] High-salinity wastewater typically refers to wastewater with a salt mass fraction exceeding 1% and a complex composition, containing multiple ions (e.g., Cu). 2+ K + Ca 2+ Na + Mg 2+ CO3 2- NO3 2- Cl - SO4 2- This refers to industrial wastewater. Direct discharge of such wastewater causes serious environmental pollution, leading to water mineralization, soil salinization and eutrophication, and may accumulate heavy metals in the food chain, affecting drinking water safety. With rapid global industrial development, the discharge of high-salinity wastewater has increased significantly.

[0003] High-salinity wastewater is difficult to treat due to its complex and variable chemical composition and high concentration of inorganic salts. These inorganic salts are often toxic to microorganisms, severely impairing the efficiency of traditional biological treatment methods. With increasingly stringent national and local emission standards, especially the pursuit of zero wastewater discharge targets, the high cost and energy consumption of traditional treatment methods pose significant technical and economic challenges for enterprises implementing zero wastewater discharge.

[0004] Existing methods for treating high-salinity wastewater, such as multi-effect evaporation and multi-stage flash evaporation, mechanical vapor recompression (MVR), reverse osmosis (RO), and membrane distillation (MD), face inherent limitations:

[0005] 1. Multi-effect evaporation and multi-stage flash evaporation: High-Ca content in high-salt wastewater 2+ and Mg 2+ The high concentration of pollutants leads to severe scaling problems in the heat exchanger, which is the core processing equipment. Furthermore, the technology requires a large amount of steam as a heat source, resulting in a complex steam system process.

[0006] 2. Mechanical Vapor Recompression (MVR): Although MVR is a novel energy-saving method that reduces energy consumption by recovering and recompressing steam, its performance is directly affected by factors such as the increased boiling point of high-salinity wastewater. Higher salt content further elevates the boiling point, directly impacting the technical parameters of the steam compressor (e.g., compression ratio, suction volume, and compression power), thereby reducing energy efficiency and increasing investment and operating costs. Furthermore, this method also suffers from severe equipment scaling problems.

[0007] 3. Reverse Osmosis (RO): RO is a widely used membrane desalination technology, but its freshwater recovery rate and brine concentration capacity are significantly limited by increased osmotic pressure and membrane fouling. Under high salinity conditions, the permeate flow rate of the RO membrane decreases, requiring higher operating pressures (increasing energy consumption), accelerating membrane fouling, and reducing the desalination rate. Most industrial RO applications are limited by scaling from compounds such as silica, calcium sulfate, phosphates, fluorides, iron, or barium salts; therefore, RO is generally not suitable for treating high-concentration salt solutions.

[0008] 4. Membrane Distillation (MD): In recent years, membrane distillation has gained popularity due to its low-temperature operation, high desalination rate, and potential for utilizing low-grade heat sources. However, in practical applications, especially when treating high-salinity wastewater, membrane wetting still presents a problem, leading to a decline in permeate quality and even process failure. At high salt concentrations, particularly when the wastewater approaches saturation, salts easily crystallize on the membrane surface, forming a scaling layer that causes a sharp drop in permeate flux. Compared to pressure-driven membrane processes such as reverse osmosis (RO), membrane distillation typically has a relatively low permeate flux. Furthermore, heat conduction losses result in high energy consumption. The technology remains in the laboratory research stage, and commercialization is still some time away.

[0009] The "zero wastewater discharge" policy has driven the development of transformative technologies. However, traditional multi-effect evaporation (MEE) and medium-volume refrigerant (MVR) are energy-intensive and expensive in achieving zero wastewater discharge. Reverse osmosis (RO) is constrained by osmotic pressure and scaling issues under high salinity conditions. While medium-volume refrigerant (MD) shows promise due to its low-temperature operation and high desalination rate, it still faces challenges related to flux and crystallization under ultra-high salinity conditions and remains in the laboratory research stage. Simply making incremental improvements to existing technologies is insufficient to meet the economic and sustainability requirements of the high-salinity wastewater zero-discharge market. Therefore, developing new methods to solve the problems of high energy consumption and scaling in high-salinity wastewater concentration under extreme concentrations is crucial.

[0010] Meanwhile, high-temperature evaporation and concentration implies a greater demand for high-grade energy, increased pollutant volatilization, and more severe scaling problems. Therefore, low-temperature evaporation and concentration represents a new direction for the development of evaporation and concentration technology. Improving the heat and mass transfer coefficient and increasing the heat exchange area are key to achieving low-temperature evaporation and concentration of high-salinity wastewater. Direct contact between the heated evaporation medium and the high-salinity wastewater for heat and mass transfer can significantly enhance the process, and a large evaporation surface area can increase the evaporation rate per unit volume. However, at high salt concentrations, scale formation on the evaporation surface can affect stable operation and reduce the heat and mass exchange area. Therefore, a novel method for evaporating and concentrating high-salinity wastewater is urgently needed that can increase the heat and mass transfer coefficient and increase the specific surface area while inhibiting scale formation on the evaporation surface to achieve a high evaporation rate without compromising the integrity of the water film on the evaporation surface and the long-term stability of surface properties. Summary of the Invention

[0011] In view of this, the present invention provides a multi-disc water film concentrator and a method for evaporating and concentrating low-temperature high-salt wastewater. The concentrator can efficiently and at low temperature evaporate and concentrate ultra-high-salt wastewater to near-saturation levels, while effectively avoiding scaling and contamination on the evaporation surface. Furthermore, by optimizing the flow channel design, material selection, and disk surface modification, the integrity of the water film is ensured and the evaporation of the water film is promoted to maximize the energy efficiency of low-temperature evaporation.

[0012] To achieve the above objectives, the present invention provides a multi-disc water film thickener, comprising a shell and a disc assembly. The shell has a liquid storage tank inside, and an inlet for introducing high-salt wastewater to be treated into the liquid storage tank. The disc assembly is rotatably mounted inside the shell and located in the liquid storage tank via a central shaft. An air inlet and an air outlet are respectively provided on opposite sides of the shell, and the air inlet and air outlet are respectively located at the two ends of the central shaft. A salt settling tank is provided below the liquid storage tank and communicates with it. A salt pushing spiral is provided laterally inside the salt settling tank, and an inclined salt discharging spiral is provided at the outlet of the salt pushing spiral. The inlet of the salt discharging spiral is lower than the outlet, and the inlet of the salt discharging spiral communicates with the outlet of the salt pushing spiral. The outlet of the salt discharging spiral is higher than the liquid level in the liquid storage tank.

[0013] The disk assembly includes multiple disks stacked parallel to each other along the central axis. The disks have hydrophilic surfaces that facilitate the formation of a uniform water film and promote the evaporation of water from the film. Disk gaps are formed between adjacent disks, and a turning channel is formed between the disks and the internal cavity of the housing. Half of the disks are immersed in wastewater in the storage tank, and half are exposed above the wastewater surface. The disk gaps and turning channels above the wastewater surface form a serpentine channel. As the disk assembly rotates, the wastewater in the storage tank forms a uniform water film on the disk surface. The water film on the disk surface above the wastewater surface undergoes direct contact heat exchange and evaporation with the hot airflow flowing through the disk gaps. When the disks rotate back below the wastewater surface, the water film on the disks evaporates completely.

[0014] A disk brush is provided in the gap between the disks. One end of the disk brush is movably connected to the central shaft, and the other end is connected to the inner wall of the housing. The disk brush brushes all areas of the disk except the central shaft during the rotation of the disk.

[0015] Hot air entering through the air inlet flows through a serpentine channel. As the hot air flows through the gaps between the discs, it evaporates the water film on both sides of the discs. As the humidity of the hot air gradually increases and the temperature gradually decreases, the low-humidity hot air eventually transforms into high-humidity warm air and is discharged from the air outlet.

[0016] Preferably, the material of the disk is a corrosion-resistant metal, polyetheretherketone, polyetherimide, polyphenylsulfone / polysulfone, G-11 / FR-5 glass epoxy composite laminate, glass fiber or carbon fiber reinforced engineering plastic.

[0017] Preferably, the disk is processed into a thin sheet structure.

[0018] Preferably, the disk surface is modified to improve hydrophilicity, and the modification treatment includes anodizing, plasma treatment, corona treatment, surface etching, dip coating, or chemical grafting.

[0019] Preferably, the hydrophilic surface of the disk is loaded with titanium dioxide nanoparticles, which are loaded by dip coating, sol-gel method, hydrothermal method or chemical grafting method.

[0020] Preferably, the disc brush includes a support rod and a hanging ring. The support rod is provided with a brush on its outer periphery, and the hanging ring is rotatably mounted on both ends of the support rod via a rotating support base.

[0021] The low-temperature high-salinity wastewater evaporation and concentration method provided by this invention includes the following steps:

[0022] a. Pre-treat high-salinity wastewater to remove suspended solids and colloids;

[0023] b. High-salt wastewater with suspended solids and colloids removed is introduced into a preheating and condensing device. The condensation and recovery concentrator discharges distilled water while raising the wastewater temperature.

[0024] c. Introduce the pretreated and preheated high-salt wastewater into the multi-plate water membrane thickener described above;

[0025] d. In the multi-disc water film condenser, the low-humidity hot air introduced by the air inlet flows in a serpentine manner in the gap between the discs and the turning channel. Through the water vapor partial pressure difference and temperature difference formed between the water film and the hot air on both sides of the gap between the discs, the water in the water film is driven to evaporate at low temperature and enter the hot air flow. Finally, the high-humidity warm air is discharged from the multi-disc water film condenser through the exhaust port.

[0026] e. The high-humidity warm air discharged from the multi-plate water film condenser then enters the preheating and condensing unit to form distilled water;

[0027] f. As the concentration process continues, the concentration of high-salt wastewater in the storage tank increases continuously, eventually forming a concentrated solution when the target concentration or close to the saturation concentration is reached.

[0028] g. Collect the distilled water;

[0029] f. Discharge the concentrated solution.

[0030] Preferably, the pretreatment in step a includes coagulation, sedimentation, and / or sand filtration.

[0031] Preferably, the low-temperature evaporation in step d is carried out under conditions where the inlet air temperature is between 60°C and 150°C.

[0032] Preferably, the low-temperature evaporation utilizes a low-grade heat source.

[0033] As can be seen from the above technical solutions, compared with the prior art, the multi-disc water film concentrator and its low-temperature high-salt wastewater evaporation and concentration method provided by the present invention have the following beneficial effects:

[0034] 1. High energy efficiency: This invention achieves high-efficiency operation at low temperatures through direct contact heat and mass transfer and multi-disc design, which greatly reduces specific energy consumption, making it more economical than MEE, MVR, high-pressure RO and MD systems, and optimizes the utilization of low-grade waste heat.

[0035] 2. High concentration ratio: This invention can concentrate high-salt wastewater to near saturation or even crystallization conditions, while continuously producing desalinated distilled water with a desalination rate of nearly 100%.

[0036] 3. Avoids scaling: This invention combines optimized disc surface materials and a real-time scrubbing strategy to minimize scaling and contamination on the evaporation surface, maintaining a high concentration ratio even when concentrating high-concentration brine.

[0037] 4. Reduced environmental impact: This invention can promote zero discharge of industrial wastewater, minimize the pollution of the environment by high-salinity wastewater, and recycle salt resources.

[0038] 5. Compactness and scalability: The small-gap multi-disc structure of this invention provides an excellent evaporation area to volume ratio, thereby achieving a compact footprint and easy large-scale expansion to meet various processing capacity requirements.

[0039] Other technical effects of the present invention are specifically described through the following embodiments. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the overall structure of the multi-disc water film concentrator of the present invention;

[0042] Figure 2 This is a cross-sectional view of the internal structure of the multi-disc water film concentrator of the present invention;

[0043] Figure 3 This is an enlarged view of the disc structure of the multi-disc water film concentrator of the present invention;

[0044] Figure 4 The diagram shows the overall system architecture and control system of the multi-plate water membrane thickener of the present invention integrated into a high-salt wastewater treatment plant.

[0045] Explanation of the attached diagram labels: Air inlet-1, Liquid inlet-2, Liquid storage tank-3, Disc-4, Disc brush-5, Disc brush hook-6, Salt settling tank-7, Diverting channel-8, Exhaust outlet-9, Salt pushing spiral-10, Salt discharging spiral-11. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of an exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] Example 1:

[0048] like Figures 1-3As shown, this invention discloses a multi-disc water film concentrator, comprising a disc assembly consisting of multiple discs 4. These discs 4 are arranged in a stacked manner within the concentrator to optimize heat and mass transfer while providing a large evaporation area, achieving low-temperature, high-efficiency evaporation and concentration of high-salt wastewater. Uniform flow channel gaps (disc gaps) are formed between the stacked discs 4 within the concentrator to optimize the flow of hot air on the surface of the water film on the discs and promote turbulence to minimize temperature and concentration polarization effects. Half of the discs 4 are immersed in the wastewater in the storage tank 3, and the other half are exposed above the wastewater surface. The disc gaps above the surface and the turning flow channel 8 form a serpentine channel. The hot airflow for wastewater evaporation is introduced into the concentrator through the air inlet 1, flows through the serpentine channel formed by the disc gaps and the turning flow channel 8, and is discharged from the concentrator through the air outlet. When the disk 4 rotates below the wastewater surface, its surface is wetted. When the disk 4 rotates above the wastewater surface, a water film forms on both sides of the disk 4. The water film on the surface of the disk 4 above the wastewater surface undergoes direct contact heat exchange and evaporation with the hot airflow flowing through the gaps between the disks. When the disk 4 is about to rotate back below the wastewater surface, the water film on the disk 4 evaporates completely, and the next coating and evaporation cycle is repeated. As the water in the wastewater is continuously carried and evaporated by the disk 4 through the water film, the salt concentration in the wastewater continuously increases until the target concentration is reached, achieving a high-rate concentration of high-salt wastewater. During this process, the wastewater raw material is continuously replenished through the inlet 2 to maintain the water level in the storage tank 3 above the lowest point of the central axis of the disk 4 (usually near the center line of the axis), preventing short-circuiting of the hot airflow. This concentrator utilizes low-temperature flue gas or airflow flowing through the gaps between stacked discs to directly exchange heat and transfer water vapor with the water film on the surface of disc 4. The arrangement of multiple discs with small gaps significantly increases the effective evaporation area of ​​the water film per unit volume and enhances turbulent flow within the gaps, thereby achieving high evaporation efficiency under low temperature differences. The selection of surface materials and optimization of surface modification for disc 4 ensure the uniformity and integrity of the water film and minimize surface binding energy. Combined with the flexible disc brush 5, it removes primary grains and contaminants from the surface of disc 4 in real time, preventing scaling and contamination on the disc 4 surface.

[0049] In this embodiment, the concentrator adopts hot air direct contact distillation to reduce mass transfer resistance and heat loss, and increase the evaporation rate per unit area. A salt settling tank 7 is provided below the liquid storage tank 3 and communicates with it. A salt pushing spiral 10 is provided in the salt settling tank 7 along the horizontal direction. An inclined salt discharging spiral 11 is provided at the outlet of the salt pushing spiral 10. The inlet of the salt discharging spiral 11 is lower than the outlet. The inlet of the salt discharging spiral 11 is connected to the outlet of the salt pushing spiral 10. The outlet of the salt discharging spiral 11 is higher than the liquid level in the liquid storage tank 3.

[0050] In this embodiment, the discs 4 are circular or polygonal, and these discs 4 are stacked concentrically and parallelly at equal intervals on the same central axis. The central axis is connected to the output end of a motor via gears and chains, and the motor drives the rotation of the central axis. Equally spaced small gaps (e.g., 3-8 mm) are left between the discs 4 to facilitate turbulent flow of hot air in the narrow channels. The evaporation medium flows directly through the small gaps between the discs 4, resulting in strong convective heat and mass transfer with the water film on the surfaces of the discs 4 on both sides. Compared with classic tubular or plate-type indirect heat transfer evaporation structures, this structure significantly increases the evaporation surface area per unit volume and the heat and mass transfer coefficient, significantly improving the performance of low-temperature distillation and concentration of high-salt wastewater.

[0051] The disk 4 used is made of a corrosion-resistant, hydrophilic metal or a high-strength, hydrophilic composite material, such as aluminum alloy, polyether ether ketone (PEEK), polyetherimide (PEI), polyphenylene sulfone (PPSU) / polysulfone, G-11 / FR-5 glass epoxy composite laminate, and glass fiber and carbon fiber reinforced engineering plastics. Except for aluminum alloy, which has good hydrophilicity after surface anodizing, other polymer materials need to improve their hydrophilicity through surface modification or loading TiO2 nanoparticles. These hydrophilic surface materials or modified hydrophilic surface materials can promote full wetting and efficient evaporation of water.

[0052] High-salt wastewater enters the concentrator through inlet 2. By adjusting the inlet flow rate and the water level in the concentrator's storage tank 3 (keeping the liquid level near the center line of the central axis of the discs 4), the lower half of the stacked discs 4 is always submerged below the liquid surface. As the discs 4 rotate, the upper half of the discs 4, fully wetted with wastewater, is always exposed above the liquid surface and enters the hot air purging area. As hot air (e.g., 60℃-150℃, or even higher) flows through the gaps (e.g., 3mm-8mm) of the discs 4, the water film on the discs 4 evaporates rapidly. Before re-entering the liquid, the discs 4 form a dry, low-water surface and are re-immersed in the storage tank 3 with rotation. After re-wetting the surface and forming a water film, they enter the next cycle. The multi-disc stacking design of the disc assembly allows the hot air to form tortuous or serpentine flow channels in the gaps between multiple discs 4 and the turning channels 8, promoting turbulent flow (high Reynolds number) and enhancing the heat and mass transfer process to maximize the evaporation capacity of the hot air.

[0053] During the operation of the concentrator, wastewater continuously flows in from the inlet 2, and the outlet of the storage tank 3 remains closed. It is only discharged once when the concentrate reaches the specified concentration. During the discharge, both the inlet 2 and the air inlet 1 are closed. After the concentrate is discharged, the wastewater inlet is reopened. During the inlet, the outlet of the storage tank 3 remains closed again until the specified liquid level is reached. Then, the air inlet is reopened to allow air to enter, and the next cycle begins.

[0054] The stacked arrangement of the discs 4 maximizes the effective evaporation surface area within a compact space. The water film formed by the wetting of the discs 4 helps to shorten the internal migration path of water molecules during the evaporation process, thereby improving evaporation efficiency. Precise speed control and flow channel design optimize the vapor pressure difference on the water film, which is the main driving force for maintaining high evaporation efficiency.

[0055] Example 2:

[0056] Optimized operation of multi-disc water film concentrators relies on online detection and precise control of various parameters to ensure stable performance and high efficiency while preventing scaling and contamination on the disc surfaces.

[0057] Multi-disc membrane evaporators achieve moisture evaporation by using low-humidity hot air flowing through the gaps between discs 4 and forming a strong heat and mass transfer with the water film on the discs 4. The hot air temperature is typically between 60℃ and 150℃, but in reality, there is no upper limit to the hot air temperature. Considering the use of lower-grade heat sources, the lower limit can be even lower. Relatively speaking, maintaining the dryness of the hot air is crucial.

[0058] The rotational speed of disc 4 is also a key operating parameter. Excessive speed can result in an overly thick water film on the disc, which is easily blown off by the high-speed hot air flow, forming droplets that enter the airflow and causing salt loss and deterioration of the recovered water quality. Insufficient speed results in an overly thin water film on the disc, reducing evaporation time utilization and thus evaporation efficiency, and also causing crystallization on the surface of disc 4. The specific rotational speed needs to be set according to the specific wastewater properties and hot air parameters. In actual operation, intelligent control can be implemented based on airflow, exhaust humidity, and the salinity change rate of the storage tank 3.

[0059] Intelligent control systems need to take into account disturbances (such as changes in hot air temperature and humidity) and adjust operating parameters (such as feed flow rate, disc rotation speed, etc.) to maintain optimal performance.

[0060] The intelligent control system can monitor the inlet air temperature and humidity, exhaust air temperature and humidity, operating pressure, hot air flow rate, liquid storage tank conductivity and pH value in real time, and dynamically adjust the operating parameters of the concentrator according to the preset algorithm or model prediction control. The key operating parameter settings are shown in Table 1.

[0061] Table 1 Key Operating Parameter Settings

[0062]

[0063] Example 3:

[0064] In the concentration process of high-salinity wastewater, especially when approaching saturation concentration, scaling and blockage of the concentrator discs clogging the air ducts and crystallization and caking in the storage tank are the main challenges to the long-term stable operation of the concentrator. This invention effectively alleviates / solves these problems through the following multifaceted strategies:

[0065] 1. Disk Material Selection and Surface Modification: Select disk materials with excellent corrosion resistance and hydrophilicity, or modified materials with good hydrophilicity (such as anodized aluminum alloys, surface-modified PEEK, PEI, PPSU / PU, G-11 / FR-5, glass fiber and carbon fiber reinforced engineering plastics, etc.) to promote water wetting and water film formation on the disk surface and reduce grain adhesion. Another important reason for choosing these materials is their low density, which facilitates lightweighting of the equipment. Considering cost, any corrosion-resistant material that has been surface-modified to be hydrophilic is also suitable.

[0066] 2. Fluid dynamics optimization: The serpentine design of the flow channel and precise control of the geometry and velocity of the hot air flow channel can generate high shear force on the surface of the water film on the disk, thereby effectively inhibiting the deposition and adhesion of primary microcrystals in the water film on the surface of disk 4, promoting the detachment of crystal nuclei from the disk surface and their entry into the bulk solution, thus reducing the risk of scaling and clogging on the surface of disk 4.

[0067] 3. Control of Local Supersaturation on the Disc: During the water film distillation process on the disc, the solute concentration near the disc surface increases due to water evaporation, leading to local supersaturation and crystallization. This invention aims to minimize the local concentration polarization effect by optimizing the water film thickness, disc rotation speed, flow channel design, and temperature control, thereby reducing the tendency for crystallization on the disc surface.

[0068] 4. In-line disk brushing: The integrated in-line disk brush 5 is crucial for maintaining the anti-scaling performance of the disk 4 surface. The disk brush 5 includes a rotating support base, a support rod, a nylon brush (or other soft-bristled brush), and a hanging ring. The nylon brush covers the outer circumference of the support rod, and the hanging rings are rotatably mounted on both ends of the support rod via the rotating support base. One end of the disk brush 5 is movably connected to the central shaft via the hanging ring, or by other overlapping methods, and the other end is connected to the disk brush hook 6 on the inner wall of the concentrator housing via the hanging ring. During the rotation of the disk 4, the nylon brush cleans all areas of the disk 4 except for the central shaft. Each rotation of the disk 4 ensures that the entire disk surface is cleaned once. Because the nylon brush can rotate around the support point, has a tight fit, and is flexible, it ensures good cleaning effect while avoiding wear on the nylon brush.

[0069] 5. Pretreatment and Chemical Additives: Although the concentrator involved in this invention has relatively lenient requirements for feed water quality, appropriate pretreatment (such as coagulation, sedimentation, and sand filtration) can significantly reduce particulate matter and colloids entering the concentrator unit, thereby reducing the fouling load. For specific scaling substances, scale inhibitors can be added as needed, but their potential impact on the performance of disc 4 should be noted.

[0070] 6. Storage Tank Cleaning Control: The integrated online disc brush 5 in storage tank 3 is crucial for preventing salt buildup in storage tank 3, maintaining continuous discharge of concentrate, and ensuring stable system operation. Storage tank 3 cleaning control typically includes salt buildup detection, pre-soaking, low-saturation wastewater cleaning (to dissolve scale salts and minerals), and high-pH cleaning (to remove organic matter, biological materials, and clay). Cleaning frequency can be dynamically triggered based on concentrate discharge performance indicators (e.g., a 10% decrease in discharge volume or a 15% increase in pump differential pressure).

[0071] Example 4:

[0072] The present invention utilizes the above-mentioned multi-disc water film concentrator for the evaporation and concentration of low-temperature, high-salt wastewater, comprising the following steps:

[0073] a. Pretreatment of high-salinity wastewater (including coagulation, sedimentation and / or sand filtration) to remove suspended solids and colloids;

[0074] b. High-salt wastewater with suspended solids and colloids removed is introduced into a preheating and condensing device. The condensation and recovery concentrator discharges distilled water while raising the wastewater temperature.

[0075] c. Introduce the pretreated and preheated high-salt wastewater into the multi-plate water membrane thickener described above;

[0076] d. In the multi-disc water film condenser, the low-humidity hot air introduced by the air inlet 1 flows in a serpentine manner in the gap between the discs and the turning channel 8. Through the water vapor partial pressure difference and temperature difference formed between the water film and the hot air on both sides of the gap between the discs, the water in the water film is driven to undergo low-temperature evaporation at an air inlet temperature of 60°C to 150°C (low-grade heat sources such as industrial waste heat, solar energy or geothermal energy can be used) and enter the hot air flow. Finally, the high-humidity warm air is discharged from the multi-disc water film condenser through the air outlet 9.

[0077] e. The high-humidity warm air discharged from the multi-plate water film condenser then enters the preheating and condensing unit to form distilled water;

[0078] f. As the concentration process continues, the concentration of high-salt wastewater in storage tank 3 increases continuously, eventually forming a concentrated solution when the target concentration or close to the saturation concentration is reached.

[0079] g. Collect the distilled water;

[0080] f. Discharge the concentrated solution.

[0081] This invention uses an online scrubbing system to clean the discs in real time to avoid scaling and contamination, and a preheating and condensation mechanism to significantly improve energy efficiency. The preheating and condensation mechanism uses the latent heat of condensation of water vapor in the high-humidity exhaust air to preheat the feed wastewater. A control system is used to monitor and adjust the operating parameters of the concentrator in real time.

[0082] Using the above method, the concentrate can be concentrated to near saturation or crystallization, and the salt rejection rate of the high-purity distilled water is higher than 99.9%. This method helps to achieve zero discharge of industrial wastewater and realize resource utilization by recovering high-purity water and / or valuable salts.

[0083] Example 5:

[0084] like Figure 4 As shown, this is a high-salt wastewater concentration system composed of a multi-plate water film thickener provided by the present invention. The multi-plate water film thickener system is the core unit in the comprehensive treatment process of high-salt wastewater, aiming to achieve zero wastewater discharge.

[0085] Upstream of a multi-plate water membrane thickener, a pretreatment stage is crucial for preparing high-salinity wastewater. This stage includes physicochemical processes such as coagulation and sedimentation to remove suspended solids and colloids. Sand filtration can further remove residual suspended solids and colloids, improving feed water quality and reducing the risk of membrane fouling. This pretreatment step is particularly important given the complex and variable composition of industrial high-salinity wastewater, ensuring stable operation.

[0086] The pretreated wastewater first enters the preheating and condensation unit, where it undergoes indirect heat exchange with the high-humidity warm air discharged from the concentrator to preheat it. Simultaneously, water vapor in the high-humidity warm air discharged from the concentrator is condensed and recovered as demineralized water. To maximize the recovery of demineralized water, a secondary refrigeration and condensation unit can be added to this unit. This preheating and condensation mechanism significantly improves energy efficiency by utilizing the latent heat of condensation of water vapor in the high-humidity exhaust air to preheat the feed wastewater.

[0087] The preheated wastewater then enters a multi-disc water film thickening unit, where the high-salt wastewater wets rotating discs 4, forming a water film on the surface of the discs 4. The water film then undergoes low-temperature evaporation under hot air blowing. The multi-disc water film evaporation design is the core of this invention, providing an extremely high heat and mass transfer surface area within a compact volume.

[0088] The evaporated water vapor enters the evaporation medium (hot air). As the hot air flows through the serpentine channels within the multi-disc water film concentrator, moisture from the water film continuously enters the hot air, increasing its humidity and gradually decreasing its temperature. Finally, the hot air is discharged from the concentrator as warm, high-humidity air. In subsequent preheating and refrigeration units, the wastewater is preheated and the demineralized water is recovered through condensation. This demineralized water can be reused in industrial processes or safely discharged, contributing to water conservation.

[0089] As the concentration process continues, the brine concentration in storage tank 3 increases. When the salinity meter in storage tank 3 detects a specified concentration, the flow of wastewater into the concentrator is stopped, and the concentrate in storage tank 3 is discharged into the concentrated brine storage tank. According to the zero-discharge target, the concentrate can be further processed for salt separation and purification (e.g., crystallization to recover salt) or disposed of safely.

[0090] The system is configured to integrate with existing industrial processes, utilizing low-grade waste heat (e.g., from tail gas or waste heat airflow) as the primary energy source for the concentrator, significantly reducing operating costs.

[0091] This invention takes the efficiency of low-grade energy utilization as a core consideration in its design, aiming to maximize the utilization of low-grade heat sources and recover energy, thereby significantly reducing operating costs. It has the following technical features:

[0092] 1. Utilization of Low-Grade Heat Sources: The core drying mechanism of this concentrator is the high-dryness evaporation water film of the evaporation medium. Therefore, the multi-disc water film concentrator designed in this invention can operate at relatively low temperatures (e.g., 60-80°C or even lower), enabling it to effectively utilize low-grade heat sources such as industrial waste heat, solar energy, or geothermal energy. This capability gives it a significant advantage in energy consumption compared to traditional high-temperature distillation or high-pressure reverse osmosis.

[0093] 2. Large Evaporation Surface Area Design: The multi-disc stacked arrangement of the evaporation surface is key to achieving low-temperature, high-efficiency evaporation. Combining the ultra-thin water film on the discs (significantly reducing the resistance to internal water migration) and the tiny gaps between the discs (ensuring high air velocity within the gaps), the heat and mass transfer coefficient can be greatly improved, enhancing water evaporation and steam transfer, thereby achieving higher evaporation rates with low-grade heat input.

[0094] 3. System heat recovery mechanism: The high-humidity hot air discharged from the concentrator can be heated by the heat exchanger to recover the latent heat of steam from the feed wastewater, thereby saving condensation energy consumption and increasing the wastewater temperature to achieve significant energy-saving effect.

[0095] 4. System Integration and Optimization: The entire wastewater treatment system is not a simple connection of a series of independent unit operations, but rather a coupled integration of multiple units. This invention emphasizes the optimized integration of the multi-disc water film thickening unit with upstream pretreatment, industrial waste heat, and downstream concentrate treatment to achieve maximum energy efficiency for the overall system. By dynamically adjusting operating parameters through a precise control system (such as online salinity model predictive control), energy consumption can be further optimized to adapt to different feed, air intake conditions, and concentration requirements.

[0096] This invention not only focuses on efficient wastewater concentration, but also strives to achieve resource recovery and maximize environmental benefits to meet increasingly stringent environmental regulations and sustainable development goals, and can achieve the following effects:

[0097] 1. Desalinated Water Recovery: Multi-plate water film concentrators can produce desalinated distilled water with a salt rejection rate of over 99.9%. This desalinated water can be directly reused in industrial production processes, such as process feedwater, cooling water, or cleaning water, thereby reducing the demand for fresh water resources and lowering the company's operating costs and water consumption.

[0098] 2. Recovery of Valuable Salts: The concentrate can be concentrated to near saturation or a crystalline state. As the wastewater is concentrated to near saturation or even the crystallization point, the concentration of dissolved salts in the concentrate is extremely high. For wastewater containing valuable minerals such as sodium, potassium, and calcium salts, these salts can be further separated, purified, and recovered from the concentrate through precipitation and crystallization processes. These salts can then be reused as industrial raw materials or byproducts, thereby transforming waste into resources and creating new economic value.

[0099] 3. Zero Wastewater Discharge: This invention significantly reduces the volume of liquid waste requiring final disposal by efficiently concentrating wastewater, providing key technological support for achieving zero industrial wastewater discharge. This helps avoid environmental problems caused by traditional high-salinity wastewater discharge, such as water mineralization, soil salinization, and heavy metal pollution.

[0100] 4. Low environmental risk: Compared with traditional thermal evaporation and reverse osmosis technologies, this invention operates at lower temperatures and atmospheric pressures and is less sensitive to feed water quality, thereby reducing the risk of equipment corrosion and failure, and minimizing chemical consumption and the generation of secondary pollutants. This helps improve the environmental safety of wastewater treatment systems.

[0101] 5. Achieving Sustainable Development: Through energy-efficient operation, water recycling, and waste resource utilization, this invention aligns with the principles of circular economy and sustainable development. It helps reduce the environmental burden of industry, promotes cleaner production, and provides an innovative solution to the global water shortage problem.

[0102] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the 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 disclosed herein.

Claims

1. A multi-disc water film concentrator, characterized in that, The device includes a housing and a disc assembly. The housing has a liquid storage tank (3) inside and an inlet (2) for introducing high-salt wastewater to be treated into the liquid storage tank (3). The disc assembly is rotatably mounted inside the housing and located in the liquid storage tank (3) via a central shaft. An air inlet (1) and an air outlet (9) are respectively provided on opposite sides of the housing. The air inlet (1) and the air outlet (9) are respectively located at the two ends of the central shaft. A salt settling tank (7) is provided below the liquid storage tank (3) and communicates with it. A salt pushing spiral (10) is provided in the salt settling tank (7) along the transverse direction. An inclined salt discharge spiral (11) is provided at the outlet of the salt pushing spiral (10). The inlet of the salt discharge spiral (11) is lower than the outlet. The inlet of the salt discharge spiral (11) is connected to the outlet of the salt pushing spiral (10). The outlet of the salt discharge spiral (11) is higher than the liquid level in the liquid storage tank (3). The disk assembly includes multiple disks (4) stacked parallel to each other along the central axis. The disks (4) have a hydrophilic surface that facilitates the formation of a uniform water film and promotes the evaporation of water from the water film. A disk gap is formed between adjacent disks (4). A turning channel (8) is formed between the disks (4) and the internal cavity of the shell. Half of the disks (4) are immersed in the wastewater in the storage tank (3), and half are exposed above the wastewater surface. The disk gaps and turning channels (8) above the wastewater surface form a serpentine channel. As the disk assembly rotates, the wastewater in the storage tank (3) forms a uniform water film on the surface of the disks (4). The water film on the surface of the disks (4) above the wastewater surface undergoes direct contact heat exchange and evaporation with the hot airflow flowing through the disk gaps. When the disks (4) rotate back below the wastewater surface, the water film on the disks (4) evaporates completely. A disk brush (5) is provided in the gap between the disks. One end of the disk brush (5) is movably connected to the central shaft, and the other end is connected to the inner wall of the housing. The disk brush (5) brushes all areas of the disk (4) except the central shaft during the rotation of the disk (4). The hot air entering through the air inlet (1) flows through the serpentine channel. When the hot air flows through the gap between the discs, it evaporates the water film on the discs (4) on both sides. As the humidity of the hot air gradually increases and the temperature gradually decreases, the low-humidity hot air eventually turns into high-humidity warm air and is discharged from the air outlet (9).

2. The multi-disc water film concentrator according to claim 1, characterized in that, The materials used for the disk (4) are corrosion-resistant metals, polyether ether ketones, polyetherimides, polyphenylene sulfones / polysulfones, G-11 / FR-5 glass epoxy composite laminates, glass fiber or carbon fiber reinforced engineering plastics.

3. The multi-disc water film concentrator according to claim 1, characterized in that, The disk (4) is processed into a thin sheet structure.

4. The multi-disc water film concentrator according to claim 1, characterized in that, The surface of the disk (4) is modified to improve its hydrophilicity. The modification treatment includes anodizing, plasma treatment, corona treatment, surface etching, dip coating or chemical grafting.

5. The multi-disc water film concentrator according to claim 1, characterized in that, The hydrophilic surface of the disk (4) is loaded with titanium dioxide nanoparticles, which are loaded by dip coating, sol-gel method, hydrothermal method or chemical grafting method.

6. The multi-disc water film concentrator according to claim 1, characterized in that, The disc brush (5) includes a support rod and a hanging ring. The support rod is provided with a brush on its outer periphery, and the hanging ring is rotatably mounted on both ends of the support rod by rotating the support base.

7. A method for evaporating and concentrating low-temperature, high-salt wastewater, characterized in that, Includes the following steps: a. Pre-treat high-salinity wastewater to remove suspended solids and colloids; b. High-salt wastewater with suspended solids and colloids removed is introduced into a preheating and condensing device. The condensation and recovery concentrator discharges distilled water while raising the wastewater temperature. c. Introducing the pretreated and preheated high-salt wastewater into the multi-plate water film thickener according to any one of claims 1-6; d. In the multi-disc water film concentrator, the low-humidity hot air introduced by the air inlet (1) flows in a serpentine manner in the disc gap and the turning channel (8) of the multi-disc water film concentrator. Through the water vapor partial pressure difference and temperature difference formed between the water film and the hot air on both sides of the disc gap, the water in the water film is driven to evaporate at low temperature and enter the hot air flow. Finally, the high-humidity warm air is discharged from the multi-disc water film concentrator through the air outlet (9). e. The high-humidity warm air discharged from the multi-plate water film condenser then enters the preheating and condensing unit to form distilled water; f. As the concentration process continues, the concentration of high-salt wastewater in the storage tank (3) increases continuously, and eventually a concentrated solution is formed when the target concentration or close to the saturation concentration is required. g. Collect the distilled water; f. Discharge the concentrated solution.

8. The method for evaporating and concentrating low-temperature, high-salinity wastewater according to claim 7, characterized in that, The pretreatment in step a includes coagulation, sedimentation and / or sand filtration.

9. The method for evaporating and concentrating low-temperature, high-salinity wastewater according to claim 7, characterized in that, The low-temperature evaporation in step d is carried out under conditions where the inlet air temperature is between 60°C and 150°C.

10. The method for evaporating and concentrating low-temperature, high-salinity wastewater according to claim 9, characterized in that, The low-temperature evaporation utilizes a low-grade heat source.

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