Low-temperature evaporation crystallization system for high-salinity wastewater

Abstract

The application relates to the technical field of high-salinity wastewater treatment, and discloses a high-salinity wastewater low-temperature evaporation crystallization system which comprises a first evaporation tower and a second evaporation tower, the first evaporation tower comprises a first heat exchange assembly and a first spraying assembly, a flow channel for circulating a heat source fluid is arranged in the first heat exchange assembly, and the first spraying assembly is used for spraying high-salinity wastewater to the outer surface of the first heat exchange assembly so that the high-salinity wastewater is evaporated to generate low-temperature steam and is concentrated; the second evaporation tower comprises a second heat exchange assembly and a second spraying assembly, the low-temperature steam generated by the first evaporation tower circulates in the interior of the second heat exchange assembly to serve as a heat source, and the second spraying assembly is used for spraying high-salinity wastewater to the outer surface of the second heat exchange assembly so that the high-salinity wastewater is evaporated and concentrated; the low-temperature steam generated by the first evaporation is used as the heat source of the second evaporation, the latent heat of evaporation of water is fully utilized, the efficient concentration of the high-salinity wastewater is realized under the condition of low temperature, and the system energy consumption is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of high-salinity wastewater treatment technology, and more specifically to a low-temperature evaporation and crystallization system for high-salinity wastewater. Background Technology

[0002] Currently, low-temperature evaporation crystallization technology is widely used in the field of high-salinity wastewater treatment due to its relatively low energy consumption. Existing low-temperature evaporation equipment typically uses single-effect or multi-effect evaporators, concentrating the water in high-salinity wastewater by heating. However, in actual operation, due to the complex composition and high salt content of high-salinity wastewater, crystallization and scaling easily occur on the heat exchange surfaces, leading to increased thermal resistance and decreased heat exchange efficiency. Furthermore, traditional equipment often lacks effective online anti-scaling measures, requiring frequent shutdowns for cleaning, which severely affects the continuous and stable operation and treatment capacity of the system. Therefore, there is an urgent need for a high-salinity wastewater evaporation crystallization system that can maintain efficient heat exchange and effectively inhibit scaling under low-temperature conditions. Summary of the Invention

[0003] To address the problems of low heat exchange efficiency and easy scaling during low-temperature evaporation in existing technologies, which prevent the system from operating stably for a long time, a low-temperature evaporation crystallization system for high-salt wastewater is provided. This system utilizes the latent heat of evaporation for efficient staged concentration and combines physical enhancement with ultrasonic synergistic descaling to ensure continuous and stable operation of the system.

[0004] To achieve the above objectives, the present invention provides a low-temperature evaporation and crystallization system for high-salt wastewater, comprising:

[0005] The first evaporation tower includes a first heat exchange component and a first spray component. The first heat exchange component has a flow channel inside for the flow of heat source fluid. The first spray component is used to spray high-salt wastewater onto the outer surface of the first heat exchange component so that the high-salt wastewater evaporates to generate low-temperature steam and is concentrated.

[0006] The second evaporation tower includes a second heat exchange component and a second spray component. The low-temperature steam generated by the first evaporation tower flows through the interior of the second heat exchange component as a heat source. The second spray component is used to spray high-salt wastewater onto the outer surface of the second heat exchange component to evaporate and concentrate the high-salt wastewater. The low-temperature steam condenses in the second heat exchange component to form cooling water.

[0007] Preferably, the first heat exchange component and the second heat exchange component are each independently selected from a plate heat exchange component or a tubular heat exchange component; the first heat exchange component and the second heat exchange component are each provided with a first flow channel inside for the flow of the heat source fluid or the low temperature steam, and are each provided with a second flow channel outside for the flow of the high-salt wastewater; the first flow channel and the second flow channel are physically isolated by heat exchange wall surfaces.

[0008] Preferably, the heat exchange wall surface of the first heat exchange component and / or the second heat exchange component is provided with a concave-convex reinforcement structure; the concave-convex reinforcement structure is configured to increase the heat exchange area of ​​the heat exchange wall surface and to disturb the liquid film of the high-salt wastewater flowing through the heat exchange wall surface.

[0009] Preferably, the plate heat exchanger assembly includes multiple parallel and spaced metal plate groups, with a second flow channel for high-salt wastewater to flow between two adjacent metal plate groups; each metal plate group includes two stacked metal plates, which are partially welded together and expanded by bubbling high-pressure fluid between them to form a regularly arranged array of circular protrusions on the surface of the metal plates, with a first flow channel for the heat source fluid or the low-temperature steam to flow between the two metal plates.

[0010] Preferably, the first heat exchange component and the second heat exchange component are respectively coupled with an ultrasonic cleaning component; the ultrasonic cleaning component includes an ultrasonic generator and a waveguide structure, the waveguide structure connecting the ultrasonic generator and the heat exchange wall surface, for transmitting ultrasonic energy to the heat exchange wall surface for anti-scaling cleaning.

[0011] Preferably, the waveguide structure includes a plurality of connectors arranged at equal intervals along the edge of the first heat exchange component or the second heat exchange component. Each connector is connected to a different horizontal position inside the corresponding heat exchange component through a waveguide tube, so that the ultrasonic energy is evenly distributed on the heat exchange wall surface of the corresponding heat exchange component.

[0012] Preferably, the first spray assembly includes a water distributor or spray nozzle located above the first heat exchange assembly, and the second spray assembly includes a water distributor or spray nozzle located above the second heat exchange assembly; both the bottom of the first evaporation tower and the second evaporation tower are provided with a collection hopper or concentrated liquid outlet for collecting the high-salt wastewater after evaporation and concentration.

[0013] Preferably, both the first evaporator and the second evaporator are equipped with an exhaust assembly and a demister at the top. The demister is configured to separate and collect the water mist generated by the evaporation of the high-salt wastewater, and the exhaust assembly is configured to discharge the separated gas.

[0014] Preferably, the first heat exchange component and the second heat exchange component are made of titanium or corrosion-resistant alloy.

[0015] Preferably, the high-salt wastewater low-temperature evaporation crystallization system further includes an air preheater, which is configured to preheat the air entering the first evaporation tower and / or the second evaporation tower.

[0016] Compared with existing technologies, the low-temperature evaporation crystallization system for high-salt wastewater provided by this invention utilizes a tiered thermal energy utilization architecture consisting of a first evaporation tower and a second evaporation tower connected in series. The low-temperature steam generated by the first-stage evaporation serves as the heat source for the second-stage evaporation. Combined with an internal heat source and external spray evaporation cooling heat exchange mode, the latent heat of vaporization of water is fully utilized, achieving efficient concentration of high-salt wastewater under low-temperature conditions and significantly reducing system energy consumption. Simultaneously, the system integrates a concave-convex reinforcement structure and an ultrasonic cleaning component on the heat exchange wall. The concave-convex reinforcement structure enhances heat transfer and inhibits initial crystallization by increasing the heat exchange area and disturbing the liquid film, while the ultrasonic component actively removes existing scale using cavitation effects. The synergistic effect of these two components constructs a dual dynamic anti-scaling mechanism of physical reinforcement and acoustic cleaning, effectively solving the industry problem of easy scaling and rapid heat decay on the heat exchange surface during the low-temperature evaporation of high-salt wastewater, ensuring long-term continuous and stable system operation. Furthermore, the system is equipped with optimized designs such as demisting collection, corrosion-resistant materials, and air preheating, further improving water quality, equipment lifespan, and overall energy efficiency, demonstrating significant engineering application value. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a low-temperature evaporation and crystallization system for high-salt wastewater provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the structure of a plate heat exchanger assembly provided in an embodiment of the present invention;

[0019] Figure 3 yes Figure 2 An enlarged view of position A in the middle;

[0020] Figure 4 yes Figure 2 An enlarged view of position B in the middle;

[0021] Figure 5 This is a cross-sectional view of a plate heat exchanger assembly provided in an embodiment of the present invention;

[0022] Figure 6 yes Figure 5 An enlarged diagram of position C in the middle.

[0023] Explanation of reference numerals in the attached figures:

[0024] 100, First evaporation tower; 101, Liquid injection pipe; 102, Liquid discharge pipe; 110, First heat exchange assembly; 111, First flow channel; 112, Second flow channel; 113, Heat exchange wall; 120, First spray assembly; 130, First circulating pump; 140, First pipeline; 200, Second evaporation tower; 210, Second heat exchange assembly; 220, Second spray assembly; 230, Second circulating pump; 240, Second pipeline; 310, Ultrasonic generator; 320, Waveguide structure; 321, Connector; 322, Waveguide tube; 400, Metal plate assembly; 410, Metal plate; 500, Air preheater. Detailed Implementation

[0025] To make the technical means, creative features, objectives, and effects of this invention readily understandable, the invention is further illustrated below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention.

[0026] like Figure 1 As shown in the figure, this embodiment of the invention provides a low-temperature evaporation and crystallization system for high-salt wastewater, which mainly includes a first evaporation tower 100 and a second evaporation tower 200. The two are coupled and connected by a thermal pipeline to form a cascade evaporation and concentration architecture to achieve the concentration treatment of high-salt wastewater.

[0027] The first evaporation tower 100 includes a first heat exchange component 110 and a first spray component 120. The first heat exchange component 110 has internal channels for the flow of heat source fluid. The first spray component 120 sprays high-salt wastewater onto the outer surface of the first heat exchange component 110 to evaporate the high-salt wastewater, generate low-temperature steam, and concentrate it. During this stage of evaporation, the higher-temperature heat source fluid flows in the internal channels of the first heat exchange component 110, while the high-salt wastewater to be treated is evenly distributed and sprayed onto the outer surface of the first heat exchange component 110 through the first spray component 120. It should be understood that the heat and mass transfer mechanism here is fundamentally different from the heat dissipation process of a traditional closed-loop cooling tower. In a traditional cooling tower, the evaporation of spray water mainly serves to reduce the temperature of the fluid inside the pipe. However, in this invention, the heat transfer of the heat source fluid inside the pipe is to drive the phase change evaporation of the high-salt wastewater outside the pipe. Its core purpose is to utilize the latent heat of vaporization of water to remove water and thus concentrate the high-salt wastewater, rather than simply cooling the heat source fluid. This "internal heat source, external wastewater spraying" structural layout allows high-salt wastewater to undergo rapid evaporation at relatively low temperatures. This avoids the problems of accelerated equipment corrosion and excessive energy consumption caused by high-temperature evaporation, while also making full use of low-grade heat energy. In this embodiment of the invention, the heat source fluid can be a low-grade heat source, such as industrial waste hot water or low-pressure steam.

[0028] The second evaporation tower 200 includes a second heat exchange component 210 and a second spray component 220. Low-temperature steam generated by the first evaporation tower 100 flows through the interior of the second heat exchange component 210 as a heat source. The second spray component 220 sprays high-salt wastewater onto the outer surface of the second heat exchange component 210 to evaporate and concentrate the wastewater. The low-temperature steam condenses inside the second heat exchange component 210 to form cooling water. In this embodiment, the low-temperature steam discharged from the top of the first evaporation tower 100 is not directly discharged or condensed and discarded, but is introduced into the internal flow channel of the second heat exchange component 210 as a driving heat source for secondary evaporation. When the low-temperature steam releases its latent heat of vaporization inside the second heat exchange component 210, it condenses to form condensate, and the released heat is transferred through the heat exchange wall to the externally sprayed high-salt wastewater, causing it to evaporate and concentrate again.

[0029] This design enables the cascade utilization of thermal energy. That is, after the same initial heat source energy completes its work once in the first evaporator tower 100, the remaining heat energy it carries is recycled and reused in the second evaporator tower 200 in the form of low-temperature steam.

[0030] It should be noted that, although the appendix of this invention... Figure 1 The image shows two separate tower structures, but in other embodiments, the first evaporator 100 and the second evaporator 200 can also be integrated into the same shell or arranged in other ways, as long as the thermodynamic logic of two-stage evaporation in series is satisfied.

[0031] By combining the aforementioned dual-tower tiered architecture with an internal heat source and external spray mode, this embodiment of the invention constructs a closed-loop multi-stage thermal energy utilization system. Compared to single-effect evaporation, this system significantly reduces steam consumption per unit water treatment volume; compared to traditional multi-effect evaporators, this system utilizes the large gas-liquid contact area and latent heat transfer efficiency of spray evaporation to maintain an extremely high heat transfer coefficient even at low temperatures, effectively solving the technical problem of low concentration efficiency of high-salt wastewater at low temperatures, while providing a stable process foundation for the implementation of subsequent anti-scaling measures.

[0032] In this embodiment of the invention, the first evaporation tower 100 and the second evaporation tower 200 can each independently achieve the concentration treatment of high-salt wastewater. Taking the first evaporation tower 100 as an example, in specific operation, a certain volume of high-salt wastewater is first injected into the first evaporation tower 100. The first circulation pump 130 is used to draw the high-salt wastewater at the bottom of the first evaporation tower 100 along the first pipe 140 to the first spray assembly 120. The high-salt wastewater is sprayed onto the outer surface of the first heat exchange assembly 110 through the first spray assembly 120. The water in the high-salt wastewater absorbs heat and evaporates, thus concentrating the high-salt wastewater. The concentrated high-salt wastewater drips to the bottom of the first evaporation tower 100. This cycle is repeated to achieve continuous concentration of high-salt wastewater until the target concentration is reached. Then, the high-salt wastewater that has reached the target concentration is discharged, and a new batch of high-salt wastewater is injected to start a new round of treatment.

[0033] Specifically, such as Figure 1 As shown, the first evaporation tower 100 is provided with a liquid injection pipe 101 with a valve in the middle for injecting high-salt wastewater to be concentrated into it, and a liquid discharge pipe 102 with a valve at the bottom of the first evaporation tower 100 for discharging the concentrated high-salt wastewater.

[0034] Similarly, the second evaporation tower 200 is also equipped with a second circulation pump 230 and a second pipeline 240. One end of the second pipeline 240 is connected to the bottom of the second evaporation tower 200, and the other end is connected to the second spray assembly 220. The second circulation pump 230 is installed on the second pipeline 240 and is used to continuously pump the high-salt wastewater from the bottom of the second evaporation tower 200 to the second spray assembly 220. The second spray assembly 220 sprays the high-salt wastewater onto the outer surface of the second heat exchange assembly 210, so that the water in the high-salt wastewater absorbs heat and evaporates to achieve concentration.

[0035] It is understood that, in this embodiment of the invention, the top of the second evaporation tower 200 can also be connected to the air inlet of the second heat exchange component 210 via a heat pipe, so as to transport the low-temperature steam generated by the high-salt wastewater in the second evaporation tower 200 during the concentration process to the second heat exchange component 210 as a heat source.

[0036] In some embodiments, the first heat exchange component 110 and the second heat exchange component 210 are each independently selected from a plate heat exchange component or a tubular heat exchange component; the first heat exchange component 110 and the second heat exchange component 210 are each provided with a first flow channel 111 for the flow of the heat source fluid or the low-temperature steam inside, and a second flow channel 112 for the flow of the high-salt wastewater outside; the first flow channel 111 and the second flow channel 112 are physically isolated by a heat exchange wall 113.

[0037] Specifically, this spatial layout of internal and external flow channels is the structural prerequisite for achieving the evaporation and concentration function rather than simply the cooling function of this invention. The heat exchange wall 113, as the sole heat and mass transfer interface, must ensure absolute airtightness and liquid tightness to prevent the clean internal heat source fluid or low-temperature steam from mixing and contaminating with the high-concentration brine externally. Simultaneously, the physically isolated heat exchange wall 113 provides stable thermal boundary conditions for the free evaporation of the external spray liquid, allowing the high-salt wastewater to continuously absorb heat and undergo phase change at a controlled temperature. It should be understood that although this embodiment of the invention uses a plate heat exchanger as an example, in other embodiments, a tubular heat exchanger or other forms of indirect heat exchangers can also be used, as long as the requirements of independent internal and external flow channels and heat transfer through a solid wall are met.

[0038] In some embodiments, the heat exchange wall 113 of the first heat exchange component 110 and / or the second heat exchange component 210 is provided with a concave-convex reinforcement structure; the concave-convex reinforcement structure is configured to increase the heat exchange area of ​​the heat exchange wall 113 and to disturb the liquid film of the high-salt wastewater flowing through the heat exchange wall 113.

[0039] It is understood that in this embodiment of the invention, the undulating reinforced structure is not a simple roughening process, but a designed geometric topology. On the one hand, this structure significantly increases the effective heat and mass transfer area per unit projected area, directly improving the evaporation flux. On the other hand, when the high-salt wastewater film flows through these undulations, the streamlines are forced to bend and separate, forming microscale turbulent vortices in local areas. This hydrodynamic disturbance effectively reduces the thickness of the liquid film boundary layer, lowers the heat transfer resistance, and, more importantly, disrupts the hydraulic conditions for the static deposition of salt crystals on the wall surface, thereby physically inhibiting the formation of initial scaling. In short, the undulating reinforced structure reduces the load on subsequent ultrasonic cleaning and is a key element in passive scaling prevention.

[0040] like Figure 2-6 As shown, in some embodiments of the present invention, the plate heat exchange assembly includes a plurality of parallel and spaced metal plate groups 400, and a second flow channel 112 for high-salt wastewater to flow between two adjacent metal plate groups 400; each metal plate group 400 includes two stacked metal plates 410, the two metal plates 410 are partially welded together and expanded by bubbling high-pressure fluid between them to form a regularly arranged array of circular protrusions on the surface of the metal plates 410, and a first flow channel 111 for the heat source fluid or the low-temperature steam to flow between the two metal plates 410.

[0041] In this embodiment of the invention, the plurality of metal plate groups 400 can specifically adopt the following... Figure 2The wastewater is arranged vertically in either the first evaporator 100 or the second evaporator 200. The spray components in the corresponding evaporators spray the high-salt wastewater to be concentrated onto the outer surface of the metal plate assembly 400. The high-salt wastewater flows downwards across the outer surface of the metal plate assembly 400, combining... Figure 3 and Figure 4 As shown, a first flow channel 111 is formed between two adjacent metal plates 410 of each metal plate group 400. Heat source fluid or low temperature steam enters from the upper inlet and exits from the lower outlet, providing heat to evaporate the water in the high-salt wastewater and achieve the concentration of the high-salt wastewater.

[0042] In this embodiment of the invention, the circular bump array is usually arranged in an equilateral triangle or square. The ratio of bump height to plate thickness and the center-to-center distance between adjacent bumps are optimized so that the spray liquid can be forcibly divided into multiple fine streams when flowing over the plate surface and then re-converge behind the bumps. This periodic liquid film rupture and recombination process effectively eliminates the heat transfer dead zone.

[0043] It should be understood that the circular bump array is only a preferred example of a concave-convex reinforcement structure. In other embodiments, herringbone corrugations, hexagonal honeycomb protrusions, or any other regularly arranged geometric topology can be used, as long as the structure can increase the heat transfer area macroscopically and disturb the liquid film flow microscopically, it falls within the protection scope of this invention. This design, which concretizes the abstract "concave-convex reinforcement" into a specific geometric shape, not only facilitates industrial stamping manufacturing, but more importantly, provides definite physical boundary conditions for maintaining a stable thin-film evaporation state of high-salt wastewater under low-temperature evaporation conditions.

[0044] In some embodiments, to address the unavoidable problem of scale buildup during long-term operation, the first heat exchange component 110 and the second heat exchange component 210 are respectively coupled with ultrasonic cleaning components; combined with Figure 2 The schematic diagram shows that the ultrasonic cleaning assembly includes an ultrasonic generator 310 and a waveguide structure 320. The waveguide structure 320 connects the ultrasonic generator 310 and the heat exchange wall 113 to conduct ultrasonic energy to the heat exchange wall 113 for anti-scaling cleaning.

[0045] In this embodiment of the invention, the high-frequency mechanical vibration generated by the ultrasonic generator 310 does not act directly on the liquid, but is efficiently introduced into the heat exchange wall of the metal material through the waveguide structure 320, making the entire heat exchange surface a huge acoustic radiation surface. When the ultrasonic energy is transferred to the wall area with salt scale, it induces a strong cavitation effect and micro-acoustic flow shearing at the solid-liquid interface. Cavitation bubbles are generated and collapse in a very short time, generating instantaneous shock waves with pressures up to several thousand atmospheres, which is sufficient to crush and peel off the firmly attached hard salt crystals; while the micro-acoustic flow continuously washes the wall surface, preventing new crystal nuclei from settling and growing. This active cleaning mechanism perfectly complements the passive scale inhibition mechanism of the aforementioned concave-convex reinforced structure: the concave-convex structure slows down the scaling rate and extends the effective cycle of ultrasonic cleaning; ultrasonic cleaning thoroughly removes any trace amounts of salt that may remain at the bottom of the concave-convex structure, preventing them from gradually accumulating and causing channel blockage.

[0046] Therefore, this embodiment of the invention ensures process safety and the independence of the thermodynamic cycle through physical isolation of the heat exchange wall, achieves enhanced heat transfer and physical inhibition of initial scaling through a textured structure, and realizes online dynamic descaling through an ultrasonic cleaning component. These three elements are closely coupled in structure and function, and none can be omitted: without physical isolation, evaporation and concentration are impossible; without textured reinforcement, relying solely on ultrasonic waves would consume too much energy and easily damage the substrate; without ultrasonic cleaning, the textured structure would eventually be filled and rendered ineffective by salt scale. It is this synergistic design that ensures the high efficiency and stability of the low-temperature evaporation crystallization system for high-salt wastewater during long-term operation.

[0047] In this embodiment of the invention, in order to ensure that the ultrasonic cleaning effect covers the entire heat exchange area, the waveguide structure 320 includes a plurality of connectors 321 arranged at equal intervals along the edge of the first heat exchange component 110 or the second heat exchange component 210. Each connector 321 is connected to a different horizontal position inside the corresponding heat exchange component through a waveguide tube 322, so that the ultrasonic energy is evenly distributed on the heat exchange wall surface 113 of the corresponding heat exchange component.

[0048] Because plate heat exchangers typically have large longitudinal dimensions, inputting ultrasonic energy at a single location can easily lead to energy dead zones or standing wave nodes due to attenuation and interference during sound wave propagation, resulting in localized scale prevention failure. This invention addresses this by arranging multiple joints at equal intervals along the edges and guiding each joint to different depths (i.e., different horizontal positions) within the plate via independent waveguides, creating a three-dimensional acoustic energy injection network. For example, the upper joints can directly deliver energy to the easily dried-out, scale-forming top area, while the lower joints cover the bottom high-concentration brine accumulation area. This multi-point, hierarchical energy introduction method ensures that regardless of the plate size, any point on the heat exchanger wall can obtain a sound intensity threshold sufficient to induce cavitation. It should be noted that although the accompanying drawings schematically show a specific number of joints, in actual engineering applications, the specific number of joints should be adaptively adjusted according to the size and material of the heat exchanger and the power of the ultrasonic generator. The term "multiple" encompasses all possible numbers of three or more, with the core principle being to achieve continuous and uniform coverage of the energy field through a spatially discrete distribution, rather than being limited to a fixed value.

[0049] In some embodiments of the present invention, the first spray assembly 120 includes a water distributor or spray nozzle located above the first heat exchange assembly 110, and the second spray assembly 220 includes a water distributor or spray nozzle located above the second heat exchange assembly 210; the bottom of the first evaporation tower 100 and the second evaporation tower 200 are both provided with a liquid collection hopper or concentrated liquid outlet for collecting high-salt wastewater after evaporation and concentration.

[0050] Specifically, the water distributor or the spray nozzle is spatially positioned directly above the corresponding heat exchange component, ensuring that the high-salt wastewater can uniformly cover the entire heat exchange wall surface by gravity, avoiding localized overheating or increased scaling caused by dry spots. For example, the water distributor can be any device capable of uniform liquid distribution, such as a perforated tubular distributor, a trough overflow distributor, or a rotary water distributor; the spray nozzle can be a spiral nozzle, a hollow cone nozzle, or a solid cone nozzle, as long as its atomization or film-forming effect meets the evaporation heat transfer requirements. Correspondingly, the bottom liquid collection hopper has a funnel-shaped or cone-bottom structure, with its lowest point connected to a concentrated liquid outlet pipe, continuously or intermittently discharging the high-salt wastewater, which has reached the target concentration after circulation and concentration, out of the system. This "top spray, bottom collect" structural layout, combined with the internal heat source circulation mentioned above, constitutes a complete material handling closed loop, ensuring continuous and stable operation of the system under unattended conditions.

[0051] In some embodiments of the present invention, the top of the first evaporation tower 100 and the second evaporation tower 200 are both provided with an exhaust assembly and a demister. The demister is configured to separate and collect the water mist generated by the evaporation of the high-salt wastewater, and the exhaust assembly is configured to discharge the separated gas.

[0052] Specifically, the demister is typically installed before the exhaust port at the top of the tower. It may contain gas-liquid separation elements such as baffles, wire mesh demisters, or swirl plates. When humid air carrying a large number of tiny droplets passes upward through the demister, the droplets are intercepted and aggregated into larger droplets due to inertial collision or centrifugal force, falling back into the tower. This effectively prevents salt from escaping with the airflow and causing environmental pollution or corrosion of downstream equipment, while also recovering valuable condensate resources. The exhaust assembly (such as an axial flow fan or centrifugal fan) is installed after the demister or at the top outlet of the tower. It overcomes system resistance and maintains a slight negative pressure or directional airflow within the tower, ensuring that the water vapor generated by evaporation can be discharged in a timely manner, maintaining the evaporation driving force. It should be understood that although the figure shows the exhaust assembly located at the top of the tower, in other embodiments, the exhaust assembly can also be a fan placed at the end of the pipeline, as long as it can drive the airflow through the evaporation tower.

[0053] In some embodiments, considering that high-salt wastewater is generally highly corrosive, the first heat exchange component 110 and the second heat exchange component 210 are made of titanium or corrosion-resistant alloy.

[0054] Understandably, titanium exhibits excellent resistance to chloride ion corrosion due to its ability to form a dense oxide film on its surface, making it particularly suitable for treating high-salt wastewater containing sodium chloride. Corrosion-resistant alloys, such as duplex stainless steel, Hastelloy, or Monel alloys, can be flexibly selected based on the specific composition of the wastewater (e.g., pH value, specific ion concentration, temperature). While this material limitation does not involve innovation in the core thermodynamic cycle, it is the material basis for ensuring the long-term effective operation of all the aforementioned structural designs under harsh conditions, avoiding leakage risks and soaring maintenance costs due to material failure.

[0055] In some embodiments, the high-salt wastewater low-temperature evaporation crystallization system further includes an air preheater 500, which is configured to preheat the air entering the first evaporation tower 100 and / or the second evaporation tower 200. Specifically, the air preheater 500 is typically located at the bottom air inlet of the first evaporation tower 100 or the second evaporation tower 200, or on an external fresh air inlet duct. The air preheater 500 utilizes low-grade waste heat generated within the system as a heating medium, such as condensate discharged from the second heat exchange component 210, some of the humid waste gas discharged from the top of the first evaporation tower 100, or waste hot water generated from other process steps. When ambient cold air flows through the air preheater 500, it absorbs waste heat and its temperature rises before entering the evaporation tower to participate in the evaporation process. From a thermodynamic perspective, the saturated moisture content of air increases exponentially with increasing temperature. Preheated air has a higher enthalpy and greater moisture absorption potential, meaning that a unit volume of air can remove more moisture from the sprayed liquid film. Therefore, under the same air volume and spray volume conditions, preheating the intake air can significantly improve the evaporation driving force, accelerate the concentration rate of high-salt wastewater, or reduce the fan energy consumption while achieving the same evaporation volume, thus realizing the deep cascade utilization of system energy.

[0056] It should be understood that in this embodiment of the invention, the air preheater 500 is an optional functional module, not a necessary component for achieving the low-temperature evaporation and crystallization function of high-salt wastewater. Even without the air preheater 500, the dual-tower cascade evaporation and synergistic anti-scaling mechanism in the aforementioned embodiments can still operate independently and complete the wastewater treatment task. This modular design allows the system to be flexibly configured according to the actual working conditions on site: in scenarios where waste heat is available and maximum energy efficiency is desired, the air preheater 500 can be added to improve economic efficiency; in scenarios where no waste heat is available or where equipment compactness is required, this module can be omitted to simplify the system structure. Furthermore, although the figure shows the air preheater located in a specific position, in other embodiments, it can also be integrated inside the tower body, installed on the connecting ventilation duct between the two towers, or adopt various heat exchange forms such as heat pipe, plate, and tube, as long as the preheating function of the air to be treated can be achieved.

[0057] To further verify the performance of the low-temperature evaporation crystallization system for high-salinity wastewater provided by this invention in practical engineering applications, particularly its evaporation efficiency under low-temperature conditions and its long-term anti-scaling stability, the following field tests and data verification were conducted based on a high-salinity wastewater treatment project at a chemical plant. It should be understood that this embodiment aims to demonstrate the effectiveness of the technical solutions in the foregoing embodiments through specific operating data, and is not intended to limit the scope of protection of this application.

[0058] The test conditions were set as follows: Taking the first heat exchange component as an example, the heat source fluid flowing inside was industrial waste hot water at approximately 50°C, and the outer surface temperature of the heat exchange wall was maintained between 45°C and 48°C. The object to be treated was high-salt wastewater discharged from the chemical plant, with a high initial salt content and complex composition. Under stable operating conditions, the total heat transfer Q carried out by the system from the heat exchange component was measured to be 1500kW. According to the thermodynamic principle of spray evaporation and concentration, the spray liquid film absorbs heat transferred from the heat exchange wall and partially evaporates. The evaporation process absorbs the latent heat of vaporization, making the liquid film temperature lower than the wall temperature, forming a continuous driving force for heat and mass transfer. Heat dissipation mainly consists of heat carried away by evaporation, sensible heat exchange between the spray water and the air, and a small amount of heat carried away by the temperature rise of the spray water. Under the design load and stable operating conditions, especially when the ambient wet-bulb temperature is not too high, most of the heat is carried away by the latent heat of vaporization of water. The theoretical evaporation rate is calculated according to the following formula:

[0059]

[0060] in, This represents the theoretical evaporation rate per hour, expressed in kg / h. This represents the total heat exchange of the system, which is 1500kW in this test. This represents the proportion of evaporative heat dissipation to the total heat exchange. In the full evaporative cooling mode, the value is usually between 0.85 and 0.95. In this calculation, a conservative value of 0.9 is used for estimation. This represents the latent heat of vaporization of water under the current operating conditions, which is approximately 2390 kJ / kg (approximately 0.66 kWh / kg) at 45°C to 48°C. Substituting this into numerical calculations, we can obtain a conservative estimate of the theoretical hourly evaporation rate. ≈ (1500 × 0.9) / 0.66 ≈ 2045 kg / h, corresponding to a daily processing capacity of approximately 49 tons. If we assume ideal total latent heat exchange (i.e., sensible heat loss is ignored), Taking estimate 1), the theoretical upper limit is approximately 1500 / 0.66≈2273 kg / h, corresponding to a theoretical daily processing capacity of about 54 tons.

[0061] In actual continuous operation monitoring, the system's average daily evaporation and concentration of water remained stable at around 40 tons. The actual value deviated somewhat from the theoretical upper limit, mainly due to engineering factors such as fluctuations in ambient wet-bulb temperature, the unavoidable nature of sensible heat exchange in the intake air, and equipment heat dissipation losses. However, even considering these losses, the system can still achieve such a large evaporation capacity driven by a low-temperature heat source of only 50℃, fully demonstrating that the internal heat source and external spray cascade evaporation architecture adopted in this application has extremely high heat and mass transfer efficiency, effectively overcoming the technical bottlenecks of traditional low-temperature evaporators, such as small heat transfer temperature difference and slow evaporation rate.

[0062] After 30 days of continuous operation, the first evaporator tower was shut down for inspection. No obvious hard scale was found on the heat exchange wall of the first heat exchange component; only a small amount of soft, soluble salt residue remained, which could be removed with simple rinsing. Testing showed that the overall heat transfer coefficient of the heat exchange component decreased by less than 5% compared to the initial operating state. This excellent anti-fouling performance stems from the synergistic mechanism of the concave-convex reinforcement structure and the ultrasonic cleaning component in the aforementioned embodiment: on the one hand, the circular bump array on the heat exchange wall continuously generates turbulent disturbances on the downstream liquid film, disrupting the steady-state conditions of the boundary layer and making it difficult for salt crystals to obtain a stable growth substrate on the wall; on the other hand, the ultrasonic energy coupled through the waveguide structure continuously induces cavitation at the solid-liquid interface, and the generated microjets and shock waves actively strip away the tiny crystal nuclei attempting to colonize the valleys of the concave-convex structure. This dual dynamic protection mechanism of physical scale inhibition and acoustic scale removal fundamentally solves the industry problem of easy scaling and rapid heat decay on the heat exchange surface during the low-temperature evaporation of high-salt wastewater. It ensures that the system maintains efficient and stable evaporation performance throughout long-term operation, and has significant engineering application value and economic benefits.

[0063] The foregoing has shown and described the basic principles, main features, and characteristics of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low-temperature evaporation and crystallization system for high-salt wastewater, characterized in that, include: The first evaporation tower (100) includes a first heat exchange component (110) and a first spray component (120). The first heat exchange component (110) has a flow channel for circulating heat source fluid. The first spray component (120) is used to spray high-salt wastewater onto the outer surface of the first heat exchange component (110) so that the high-salt wastewater evaporates to generate low-temperature steam and is concentrated. The second evaporation tower (200) includes a second heat exchange component (210) and a second spray component (220). The low-temperature steam generated by the first evaporation tower (100) flows into the interior of the second heat exchange component (210) as a heat source. The second spray component (220) is used to spray high-salt wastewater onto the outer surface of the second heat exchange component (210) to evaporate and concentrate the high-salt wastewater. The low-temperature steam condenses in the second heat exchange component (210) to form cooling water.

2. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 1, characterized in that, The first heat exchange component (110) and the second heat exchange component (210) are each independently selected from plate heat exchange components or tubular heat exchange components; the first heat exchange component (110) and the second heat exchange component (210) are each provided with a first flow channel (111) for the flow of the heat source fluid or the low temperature steam inside, and a second flow channel (112) for the flow of the high salt wastewater outside; the first flow channel (111) and the second flow channel (112) are physically isolated by a heat exchange wall (113).

3. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 2, characterized in that, The heat exchange wall (113) of the first heat exchange component (110) and / or the second heat exchange component (210) is provided with a concave-convex reinforcement structure; the concave-convex reinforcement structure is configured to increase the heat exchange area of ​​the heat exchange wall (113) and to disturb the liquid film of the high-salt wastewater flowing through the heat exchange wall (113).

4. The low-temperature evaporation and crystallization system for high-salt wastewater according to claim 2, characterized in that, The plate heat exchange assembly includes multiple parallel and spaced metal plate groups (400), and a second flow channel (112) for high-salt wastewater to flow between two adjacent metal plate groups (400); each metal plate group (400) includes two stacked metal plates (410), the two metal plates (410) are partially welded together and expanded by bubbling high-pressure fluid between them to form a circular array of protrusions regularly arranged on the surface of the metal plates (410), and a first flow channel (111) for the heat source fluid or the low-temperature steam to flow between the two metal plates (410).

5. The low-temperature evaporation and crystallization system for high-salt wastewater according to claim 2, characterized in that, The first heat exchange component (110) and the second heat exchange component (210) are respectively coupled with an ultrasonic cleaning component; the ultrasonic cleaning component includes an ultrasonic generator (310) and a waveguide structure (320), the waveguide structure (320) connects the ultrasonic generator (310) and the heat exchange wall (113) to conduct ultrasonic energy to the heat exchange wall (113) for anti-scaling cleaning.

6. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 5, characterized in that, The waveguide structure (320) includes a plurality of connectors (321) arranged at equal intervals along the edge of the first heat exchange component (110) or the second heat exchange component (210). Each connector (321) is connected to a different horizontal position inside the corresponding heat exchange component through a waveguide tube (322) so that the ultrasonic energy is evenly distributed on the heat exchange wall (113) of the corresponding heat exchange component.

7. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 1, characterized in that, The first spray assembly (120) includes a water distributor or spray nozzle located above the first heat exchange assembly (110), and the second spray assembly (220) includes a water distributor or spray nozzle located above the second heat exchange assembly (210); the bottom of the first evaporation tower (100) and the second evaporation tower (200) are provided with a liquid collection hopper or concentrated liquid outlet for collecting high-salt wastewater after evaporation and concentration.

8. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 7, characterized in that, The top of the first evaporator (100) and the second evaporator (200) are both equipped with an exhaust assembly and a demister. The demister is configured to separate and collect the water mist generated by the evaporation of the high-salt wastewater, and the exhaust assembly is configured to discharge the separated gas.

9. The low-temperature evaporation and crystallization system for high-salinity wastewater according to claim 1, characterized in that, The first heat exchange component (110) and the second heat exchange component (210) are made of titanium or corrosion-resistant alloy.

10. The low-temperature evaporation and crystallization system for high-salinity wastewater according to any one of claims 1-9, characterized in that, It also includes an air preheater (500) configured to preheat the air entering the first evaporator (100) and / or the second evaporator (200).

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