A low-pressure steam reuse evaporation crystallization device

Abstract

This invention provides a low-pressure steam reuse evaporation crystallization device, comprising a vacuum negative pressure system, an evaporation crystallization system, and a gas-liquid separation system. The vacuum negative pressure system consists of an ejector, a centrifugal pump, a vacuum pump, and a buffer tank. It achieves a high vacuum environment within the evaporation kettle through dual-stage vacuum coordination, lowering the boiling point of the waste liquid to below 25°C. The evaporation crystallization system uses an evaporation kettle with a heat exchange jacket. A spiral scraper assembly is installed inside the kettle, driven by a motor via a sprocket and chain mechanism to rotate, achieving material stirring and inner wall crystal scraping. This invention significantly reduces evaporation energy consumption and solves problems such as severe scaling and short operating cycles in traditional equipment.

Description

Technical Field

[0001] This utility model relates to the technical field of low-temperature evaporation crystallization equipment, specifically to a low-pressure steam reuse evaporation crystallization equipment. Background Technology

[0002] Large quantities of highly concentrated organic wastewater are commonly generated during the production processes of industries such as pharmaceuticals, pesticides, bioengineering, petrochemicals, and food. This type of wastewater typically exhibits characteristics such as near-saturation salt content, high organic pollution load, and strong biochemical toxicity, requiring comprehensive treatment. Comprehensive treatment generally involves conditioning, concentration, crystallization and drying, or incineration to treat the wastewater, achieving the goals of volume reduction, stabilization, and harmlessness. Among these, evaporation, crystallization, and drying are the core processes, accounting for over 60% of the total cost of the wastewater treatment system.

[0003] Current mainstream crystallization drying equipment, such as drum dryers and paddle dryers, faces the following technical bottlenecks:

[0004] 1. High energy consumption, requiring a continuous supply of high-grade steam with a pressure greater than 0.4 MPa, resulting in high energy consumption per ton of water evaporated;

[0005] 2. High calcium and magnesium ions and high viscosity organic matter in waste liquid often lead to frequent scaling on heat exchange surfaces and material adhesion to the inner wall, resulting in a continuous operating cycle of less than 72 hours for the equipment.

[0006] 3. Insufficient stability, such as heat transfer efficiency reduction and mechanical component jamming caused by scaling, prevents the actual production capacity of the equipment from reaching the design value.

[0007] 4. There is a risk of secondary pollution, as organic matter volatilizes and dissipates during the evaporation process, increasing the burden of end-of-pipe treatment.

[0008] The aforementioned defects have led to the general abandonment of traditional equipment before it reaches its designed service life, and at the same time, it is difficult to meet increasingly stringent environmental regulations.

[0009] Energy-saving evaporation technologies that have emerged in recent years still face some application bottlenecks. For example, patent application CN202110138729.5 discloses a heat pump-driven carrier gas extraction process device for waste liquid, characterized by low evaporation energy consumption, high concentration efficiency, and high safety. This device includes a waste liquid circulation system, an extraction air circulation system, a heat pump system, and a data acquisition system. However, its reliance on a semi-permeable membrane structure cannot withstand the scouring effect of crystallizing salts, limiting its applicability to salt-free waste liquids. It has poor applicability to saline wastewater, which accounts for over 80% of industrial wastewater, and its technology lacks versatility. Another example is patent application CN201610229721.9, which discloses an industrial wastewater treatment system consisting of an air circulation microsystem, a waste liquid concentration microsystem, and a heat pump circulation microsystem. While it constructs an air circulation and heat pump coupled system, it lacks an anti-scaling mechanism, leading to localized drying failure during the waste liquid crystallization stage and resulting in very low actual crystallization efficiency. Utility Model Content

[0010] The purpose of this invention is to provide a low-pressure steam reuse evaporation crystallization device that solves the problems of high steam quality requirements, low heat transfer efficiency due to crystal adhesion, and low vacuum degree in existing evaporation crystallization devices.

[0011] To achieve the above objectives, the present invention proposes the following technical solution:

[0012] A low-pressure steam reuse evaporation crystallization device includes a vacuum negative pressure system and an evaporation crystallization system.

[0013] The vacuum negative pressure system includes an ejector, a centrifugal pump, a buffer tank, and a vacuum pump;

[0014] The jet ejector is provided with a first inlet, a second inlet, and a first outlet;

[0015] The first inlet is connected to the outlet of the centrifugal pump, the second inlet is connected to the exhaust port of the evaporation crystallization system through pipe D, and the first outlet is connected to the first inlet of the buffer water tank through pipe A.

[0016] The inlet of the centrifugal pump is connected to the first outlet of the buffer water tank via pipe B;

[0017] The inlet of the vacuum pump is connected to the gas outlet of the buffer tank via pipe C, and the outlet is connected to the external environment or connected to the gas buffer container via a gas pipe.

[0018] As a preferred technical solution of this utility model, the evaporation crystallization system includes an evaporation kettle and a condensate tank;

[0019] The evaporator has a cylindrical structure and is fitted with a heat exchange jacket on its outer side. The evaporator is provided with an exhaust port and a liquid inlet.

[0020] The heat exchange jacket forms a sealed steam chamber with the outer wall of the evaporator. The heat exchange jacket has a steam inlet and a steam outlet on its side wall. The steam inlet is connected to the steam generator through pipe F, and the steam outlet is connected to the condensate tank through pipe E.

[0021] As a preferred embodiment of the present invention, the evaporation crystallization system further includes a scraping assembly and a driving assembly;

[0022] The scraping assembly includes a stirring shaft and a spiral scraper;

[0023] The stirring shaft is coaxially arranged with the evaporator, and its two ends are movably connected to the end sidewalls of the evaporator.

[0024] The spiral scraper is sleeved on the outside of the stirring shaft in an equidistant spiral structure, with its outer edge in contact with the inner wall of the evaporation vessel and its inner edge connected to the stirring shaft through a support column.

[0025] The drive assembly is driven by the stirring shaft.

[0026] As a preferred technical solution of this utility model, the drive assembly includes a driving sprocket, a driven sprocket, a chain, and a drive motor;

[0027] The drive motor is located below one end of the evaporator;

[0028] The drive sprocket is mounted on the output shaft of the drive motor;

[0029] The driven sprocket is mounted on the end of the stirring shaft on the same side as the driving sprocket;

[0030] The chain meshes with the driving sprocket and the driven sprocket.

[0031] As a preferred technical solution of this utility model, one end side wall of the evaporator is provided with a discharge port, and a pneumatic discharge valve is installed at the discharge port.

[0032] As a preferred embodiment of this utility model, the evaporation crystallization equipment further includes a gas-liquid separation system;

[0033] The gas-liquid separation system includes a spiral separator, a porous media demister, and a condenser connected in sequence.

[0034] The inlet of the spiral separator is connected to the exhaust port of the evaporator;

[0035] The vapor outlet of the condenser is connected to the second inlet of the ejector via the pipe D.

[0036] As a preferred embodiment of this invention, the inner wall of the evaporator is coated with an anti-stick coating.

[0037] As a preferred technical solution of this utility model, the evaporation crystallization equipment further includes a waste heat recovery system;

[0038] The waste heat recovery system includes a waste heat exchanger, which includes a shell and a plurality of waste heat exchange tubes disposed inside the shell.

[0039] The working fluid inlet of the outer shell is connected to the outlet of the condensate tank;

[0040] The inlet of the waste heat exchange tube is connected to the waste liquid storage tank, and its outlet is connected to the inlet of the evaporation kettle.

[0041] As can be seen from the above technical solutions, the present invention provides a low-pressure steam reuse evaporation crystallization device, which has the following advantages compared with the prior art:

[0042] 1. By maintaining a high vacuum environment of -99 kPa inside the evaporator through a vacuum negative pressure system, the boiling point of the waste liquid is lowered to below 25°C. Only low-pressure steam below 0.3 MPa is needed to drive the evaporation process, reducing energy consumption by more than 50%. At the same time, room temperature evaporation avoids the formation of hard scale from the evaporation of calcium and magnesium ions.

[0043] 2. The scraping component can not only stir the waste liquid during the evaporation process, making it heat up evenly and evaporate quickly, but also scrape off the crystals adhering to the inner wall of the evaporation kettle after evaporation, thus improving the efficiency of evaporation and crystallization.

[0044] 3. The integrated, modular, and standardized design of the equipment greatly reduces the amount of on-site engineering work, enabling standardized production while facilitating maintenance.

[0045] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered as part of the utility model subject matter of this disclosure, provided that such concepts do not contradict each other.

[0046] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0047] The accompanying drawings are not drawn to scale according to a true reference numeral. In the drawings, each identical or nearly identical component shown in the various figures can be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0048] Figure 1 This is a front view of the evaporation and crystallization equipment according to Embodiment 1 of this utility model;

[0049] Figure 2 This is a top view of the evaporation and crystallization apparatus of Embodiment 1 of this utility model;

[0050] Figure 3 This is a left-side view of the evaporation and crystallization apparatus of Embodiment 1 of this utility model;

[0051] Figure 4 This is a right-side view of the evaporation and crystallization apparatus of Embodiment 1 of this utility model;

[0052] Figure 5 This is a front view of the evaporator of Embodiment 1 of this utility model;

[0053] Figure 6 This is a front view of the scraping assembly of Embodiment 1 of this utility model.

[0054] The meanings of the reference numerals in the figure are as follows:

[0055] 1. Frame, 2. Ejector, 3. Vacuum pump, 4. Buffer tank, 5. Centrifugal pump, 6. Pipe B, 7. Pipe D, 8. Condenser, 9. Gas-liquid separator, 10. Evaporator, 11. Pipe A, 12. Reducer, 13. Condensate tank, 14. Cylinder, 15. Viewing window, 16. Heat exchange jacket, 17. Pipe F, 18. Steam regulating valve, 19. Pipe E, 20. Stirring shaft, 21. Spiral scraper, 22. Fixed base, 23. Bearing housing, 24. Mechanical seal bearing, 25. Support column, 26. Connecting rod, 27. Drive sprocket, 28. Driven sprocket, 29. Chain, 30. Drive motor, 31. Discharge pipe, 32. Connecting pipe, 33. Negative pressure sensor, 34. Intelligent control box. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this utility model pertains.

[0057] The terms "first," "second," and similar words used in this utility model patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0058] To address the problems of high steam quality requirements, low heat transfer efficiency due to crystal adhesion, and low vacuum in existing evaporation crystallization devices, this invention proposes a low-pressure steam reuse evaporation crystallization device based on LVR (Low Vapor Reuse) evaporation crystallization technology. This evaporation crystallization system utilizes low-pressure steam reuse technology to evaporate, crystallize, and dry industrial wastewater with high concentrations of salt. It is a modular, integrated system for reducing the volume of high-concentration salt wastewater. It employs an intelligent dual-vacuum negative pressure system to create a high vacuum negative pressure state, with a vacuum degree as high as -99 kPa. Combined with a high-efficiency heat exchange jacket, only low-grade, low-pressure steam (e.g., below 0.3 MPa) is needed to provide the calorific value required for wastewater evaporation, enabling low-temperature evaporation crystallization of the wastewater at 25°C.

[0059] The process involves coating the inner wall of the evaporator with a non-stick polymer material coating, which helps the concentrated crystals or solid residues overcome viscous resistance, preventing scaling and coking in the evaporator, allowing the crystals and solid residues to be discharged smoothly, and improving the working efficiency and service life of the evaporation crystallization equipment.

[0060] Specifically, in some specific embodiments of this utility model, the coating component forming the coating includes 10% film-forming agent and 90% fluorosilicone resin. The film-forming agent, by mass, comprises the following components: 80%-90% acrylic resin, 10%-20% ethylene glycol, 1%-5% dodecyl ester, and 0.5%-2% water. The fluorosilicone resin, by mass ratio, has the following composition: perfluorododecyltrichlorosilane: n-hexane: silica: water: fluorinated modification liquid: curing butyl acetate = 3:100:3:2:95:50, wherein the silica is hydrophilic silica particles, and the fluorinated modification liquid is one or a mixture of several of the following: fluoroacrylate polymer, perfluoropolyether, polytetrafluoroethylene, etc. After the film-forming agent and fluorosilicone resin are mixed evenly, the mixture is sprayed onto the inner wall surface of the evaporator 10 using a spray gun at a constant air pressure of 0.18-0.25 bar. It can be surface dried in 5-20 minutes at room temperature and fully cured in 24 hours. It has the characteristics of low-temperature curing, good weather resistance, and excellent self-cleaning ability.

[0061] The coating of this embodiment possesses superhydrophobic (i.e., hydrophobic and oleophobic) properties, with a water contact angle of 165° and an oil contact angle of 138°. Even after immersion in a saturated salt solution for one year, it maintains a superhydrophobicity with a contact angle >150°. Cross-cut adhesion testing shows the coating's adhesion is grade 4B, meeting the adhesion technical requirements for Type II Class 1 products in HG / T 3668 standard. With a 120-micron thick coating, the acidic salt spray test shows a corrosion resistance of up to 50,000 hours. The adhesion strength between the coating surface and sodium chloride is 100 kPa, significantly lower than the 1000 kPa of stainless steel, a decrease of approximately 90%. Under shear force, sodium chloride and other salts are more likely to fracture and detach along the coating interface, using the coating as a crack initiation point, thus preventing the accumulation and adhesion of evaporated salt crystals on the spiral scraper and affecting system slag discharge.

[0062] Example 1

[0063] The low-pressure steam reuse evaporation crystallization equipment provided by this utility model includes a vacuum negative pressure system, an evaporation crystallization system, and a gas-liquid separation system. The vacuum negative pressure system is used to create a high negative pressure, such as -99 kPa, lowering the boiling point of water in the high-concentration saline waste liquid in the evaporation crystallization system to ambient temperature, such as 25°C. This allows the evaporation crystallization system to efficiently evaporate the high-concentration saline waste liquid at ambient temperature (below 0.3 MPa) using low-pressure steam as a heat source, significantly reducing energy consumption from 1.5 tons to 0.8 tons. The evaporation crystallization system is the main site for the evaporation, crystallization, and drying of the high-concentration saline waste liquid. The gas-liquid separation system is used to separate and condense the gas-liquid mixture, including water vapor, entrained liquid droplets / droplets, and non-condensable gases, generated during the operation of the evaporation and crystallization system. Specifically, the liquid droplets or droplets in the gas-liquid mixture are first separated and returned to the evaporation and crystallization system. The water vapor and non-condensable gases, after being deliquulated, enter the condenser. The water vapor is condensed to form a second condensate, while the non-condensable gases are drawn into the vacuum negative pressure system under negative pressure.

[0064] In order to achieve the modular and integrated design of the evaporation crystallization equipment, in this embodiment, as follows: Figure 1-4 As shown, the vacuum negative pressure system, evaporation crystallization system, and gas-liquid separation system are mounted on the same frame 1. The general structure of the entire evaporation crystallization equipment is as follows: the vacuum negative pressure system and piping are mainly located at the bottom of frame 1; the evaporation crystallization system is located in the middle of frame 1; and the gas-liquid separation system is located at the top of frame 1. Of course, in other specific embodiments, the positions of each system can be arranged according to the actual situation. The positional relationship of the systems described in this embodiment is not unique.

[0065] In this embodiment of the invention, the vacuum negative pressure system includes an ejector 2, a centrifugal pump 3, a buffer tank 4, and a vacuum pump 5. Specifically, the centrifugal pump 3, the buffer tank 4, and the vacuum pump 5 are all mounted on the base plate of the frame 1. The inlet of the centrifugal pump 3 is connected to the first outlet of the buffer tank 4 via pipe B 6, and the outlet of the centrifugal pump 3 is connected to the ejector 2.

[0066] The ejector 2 has a first inlet, a second inlet, and a first outlet. The first inlet of the ejector 2 is connected to the outlet of the centrifugal pump 3, which draws water from the buffer tank 4. The second inlet of the ejector 2 is connected to the gas phase outlet of the condenser 8 through pipe D 7, which is used to directly extract non-condensable gases from the condenser 8, thereby indirectly extracting gases from the evaporator 10 and maintaining a high vacuum inside the evaporator 10. The first outlet of the ejector 2 is connected to the first inlet of the buffer tank 4 through pipe A 11, which sprays the water vapor mixture into the buffer tank 4. In some specific embodiments of this utility model, the ejector 2 can be an existing Venturi ejector, the working principle and structure of which are common knowledge and will not be described in detail here.

[0067] In this embodiment of the invention, a centrifugal pump 3 draws water from the buffer tank 4 into the ejector 2. The water enters the ejector 2 at high speed and then exits from the first outlet of the ejector 2 at high speed. When the high-speed water flows through the mixing chamber of the ejector 2, it creates a vacuum in the mixing chamber inside the ejector 2. This allows the ejector 2 to use negative pressure to extract non-condensable gas from the condenser 8 through pipe D 7, thereby continuously extracting the gas generated by the evaporator 10. After the non-condensable gas enters the mixing chamber, it mixes violently with the water at the throat of the ejector 2 to form a gas-liquid mixture, which is then ejected from the first outlet of the ejector 2. The entire process forms a highly efficient negative pressure system.

[0068] The inlet of vacuum pump 5 is connected to the gas outlet at the top of buffer tank 4 via pipe C. The outlet of vacuum pump 5 can be directly connected to the external environment or connected to a gas buffer container via a gas pipe. During operation, the buffer tank 4 is not completely filled with water; a certain amount of gas phase space is reserved at the top. Vacuum pump 5 draws gas from this space, maintaining a vacuum in the buffer tank 4. It should be noted that pipe C is not shown in the figure due to the limited perspective of the attached diagram, but the connection method between pipe C and vacuum 5 is a mature and fundamental technology in this field. Those skilled in the art can easily implement it without difficulty based on the above description, and there are no technical obstacles.

[0069] Therefore, this embodiment of the invention utilizes a combination of centrifugal pump 3 and ejector 2 as a primary vacuum source, and vacuum pump 5 as a secondary vacuum source and vacuum stabilization auxiliary device, forming a dual vacuum system. This breaks through the conventional vacuum system's vacuum limit of -95 to -98 kPa, achieving a vacuum degree of -99.9 kPa. Under this state, the boiling point of high-concentration saline wastewater is below 25°C, enabling low-temperature (25°C) evaporation. Furthermore, the evaporation process of high-concentration saline wastewater is prone to fluctuations in evaporation rate, which cannot be effectively adjusted by a conventional single vacuum system, resulting in drastic fluctuations in vacuum degree. The vacuum negative pressure system of this invention achieves frequency conversion regulation through the cooperation of the dual vacuum systems, effectively addressing the matching problem between evaporation rate and vacuum degree.

[0070] This invention's dual-stage vacuum synergy mechanism achieves a breakthrough in vacuum stability through complementary physical interactions. Firstly, the ejector 2 provides efficient pumping. When the centrifugal pump 3 drives high-speed water flow through the throat of the ejector 2, a transient ultra-low pressure zone is formed in the mixing chamber according to Bernoulli's principle. This rapidly extracts a large amount of gaseous material from the evaporator 10, suitable for the explosive gas release phase of evaporation. The vacuum pump 5, as a secondary pressure stabilizing unit, maintains precise negative pressure, continuously pumping the gas phase space at the top of the buffer tank 4, eliminating vacuum fluctuations caused by fluid pulsation in the ejector 2, and ensuring the system remains stable at a high ultimate vacuum level for an extended period. When the evaporation rate changes abruptly, such as due to fluctuations in feed concentration, the vacuum pump 5 compensates for the pumping capacity shortfall of the ejector 2 through frequency conversion speed regulation, avoiding the vacuum collapse common in single-stage systems.

[0071] In this embodiment of the utility model, the evaporation crystallization system includes an evaporation kettle 10, a condensate tank 13, a scraping assembly, and a driving assembly.

[0072] Among them, such as Figure 5 As shown, the evaporator 10 is cylindrical in shape, with its outer wall fixedly connected to the middle of the frame 1 via a fixing bracket. A discharge port is provided on one end sidewall of the evaporator 10 for discharging crystalline material or crystalline residue. A pneumatic discharge valve is installed at the discharge port, which is driven to open and close by a cylinder 14. An exhaust port is also provided at the top of the evaporator 10 for discharging the gaseous mixture generated during evaporation and crystallization, and as a gas outlet for vacuuming, connected to a vacuum negative pressure system. An inlet is also provided on the evaporator 10, serving as an inlet for waste liquid or washing water. A viewing window 15 is provided on one end sidewall of the evaporator 10 for workers to observe the evaporation and crystallization state of the material inside the evaporator 10, or for installing sensing elements such as infrared sensors. To rationally arrange the discharge port and viewing window 15, in this embodiment of the invention, the discharge port is located at the rear end of the reactor 10, and the viewing window 15 is located at the front end of the reactor.

[0073] like Figure 4 As shown, a heat exchange jacket 16 is fitted around the outside of the evaporator 10, forming a sealed steam chamber between the heat exchange jacket 16 and the outer wall of the evaporator 10. The bottom of the heat exchange jacket 16 has a steam inlet and a steam outlet. The steam inlet is connected to a steam generator, such as a municipal steam pipeline or an external steam generating device, via pipe F 17. Pipe F 17 is equipped with a steam regulating valve 18 for regulating the steam flow rate. The steam outlet is connected to a condensate tank 13 located on the base plate of the frame 1 via pipe E 19. Pipe E 19 serves as the discharge pipeline for the condensate formed after low-pressure steam heat exchange. Figure 3 As shown, the condensate tank 13 and the buffer tank 4 are arranged side by side. After the low-pressure steam enters the heat exchange jacket 16 and exchanges heat with the material in the evaporator 10, condensate is formed. The condensate enters the condensate tank 13 through the pipe E 19 for temporary storage.

[0074] Among them, such as Figure 6 As shown, the scraping assembly includes a stirring shaft 20 and a spiral scraper 21. The stirring shaft 20 is coaxially disposed inside the evaporator 10, with both ends movably penetrating the end sidewalls of the evaporator. A fixing seat 22 is provided on the outer side of each end sidewall of the evaporator 10, and a bearing seat 23 is provided on the fixing seat 22. The ends of the stirring shaft 20 are rotatably connected to the bearing seats 23. A mechanically sealed bearing 24 is provided at the connection between the stirring shaft 20 and the end sidewall of the evaporator 10 to ensure the sealing of the evaporator 10 and guarantee its internal vacuum.

[0075] The spiral scraper 21 is arranged in an equidistant spiral structure around the outside of the stirring shaft 20 and extends along the axial direction of the stirring shaft 20. Unlike traditional spiral blades or impellers, the inner edge of the spiral scraper 21 in this embodiment is not directly and tightly welded to the outer wall of the stirring shaft 20, but is indirectly connected to the stirring shaft 20 through several support columns 25. Its outer edge contacts the inner wall of the evaporator 10, but is not fixedly connected. Specifically, one end of the support column 25 is fixedly connected to the outer wall of the stirring shaft 20 by welding or other means, and the other end is connected to the blade of the spiral scraper 21 by welding or riveting. This is equivalent to supporting the spiral scraper 21 on the outside of the stirring shaft 20, so that there is a gap between the inner side of the spiral scraper 21 and the outer wall of the stirring shaft 20, so that the scraping assembly has a large range of hollows. This facilitates the rapid discharge of water vapor and other gaseous mixtures during the evaporation of high-concentration waste liquid through the gaps, which is conducive to the efficient vacuuming of the vacuum negative pressure system and avoids the accumulation of water vapor and other gaseous mixtures. Adjacent support columns 25 on the same axis are connected by at least two connecting rods 26 to enhance the connection stability between the spiral scraper 21 and the stirring shaft 20.

[0076] The drive assembly includes a drive sprocket 27, a driven sprocket 28, a chain 29, and a drive motor 30. The drive motor 30 is mounted on the base plate of the frame 1, located below one end of the evaporator 10. The drive sprocket 27 is connected to the output shaft of the drive motor 30. The driven sprocket 28 is connected to the end of the stirring shaft 20 on the same side as the drive sprocket 27. The chain 29 meshes between the drive sprocket 27 and the driven sprocket 28. The drive motor 30 drives the drive sprocket 27 to rotate, which in turn drives the driven sprocket 28 to rotate via the chain 29. This, in turn, causes the stirring shaft 20 to rotate the spiral scraper 21, thus stirring the material inside the evaporator 10 and accelerating the evaporation rate of the waste liquid. After evaporation and crystallization, the crystals adhering to the inner wall of the evaporator 10 can also be scraped off, improving discharge efficiency.

[0077] To better control the drive motor 30, a reducer 12 is mounted on the output shaft of the drive motor 30 via a coupling. The output shaft of the reducer 12 is connected to the drive sprocket 27 via a key connection or other means. Preferably, the reducer 12 is a planetary gear reducer. The reducer 12 amplifies torque and controls the drive motor 30 at low speeds, protects the drive motor 30 through inertia matching to prevent overshoot during start-stop operation, and improves the overload tolerance of the drive motor 30. The model and configuration of the drive motor and reducer are common knowledge in the art, and those skilled in the art can configure them appropriately according to actual conditions; further details are omitted here.

[0078] like Figure 1 As shown, in this embodiment of the invention, the discharge port is located at the rear end of the evaporator 10 and below the end of the stirring shaft 20. To facilitate the installation of the pneumatic discharge valve, a discharge pipe 31 is also provided, with an outlet at the bottom of the discharge pipe 31. To avoid the protruding discharge pipe 31 affecting the movement of the sprocket and chain 29, the drive motor 30 is located below the front end of the evaporator 10, which has no complex structure. The space here can be used to reasonably arrange the driven sprocket 28 and chain 29.

[0079] This invention utilizes the principle that the boiling point of highly concentrated waste liquid decreases with decreasing pressure. A vacuum negative pressure system is used to create a vacuum state inside the evaporator 10, achieving a vacuum degree of approximately -99 kPa. At this pressure, the boiling point of water is below 25°C, allowing it to evaporate through low-pressure steam heating. In specific operation, low-pressure steam is used as a heat source and introduced into the heat exchange jacket 16 to heat the material inside the evaporator 10. Simultaneously, a rotating scraper assembly stirs the material, causing the water in the highly concentrated waste liquid to evaporate rapidly and evenly, while organic matter and salts are concentrated and crystallized.

[0080] If the vacuum negative pressure system is directly connected to the exhaust port of the evaporator 10, uncondensed aerosol droplets will enter the ejector 2 and vacuum pump 5, posing a risk. For example, if the vacuum negative pressure system fails, entrained organic droplets will directly enter the buffer tank 4, increasing the end-processing load and causing vacuum fluctuations. Therefore, to improve the service life and vacuum stability of the vacuum negative pressure system, this embodiment of the invention includes a gas-liquid separation system between the evaporation crystallization system and the vacuum negative pressure system.

[0081] The gas-liquid separation system includes a gas-liquid separator 9 and a condenser 8, which are connected by a connecting pipe 32. The gas-liquid separator 9 includes a spiral separator and a porous media demister connected in sequence. The spiral separator and the porous media demister can utilize existing technologies, and the porous media demister can also be replaced by a separator equipped with a semi-permeable membrane. Specifically, the inlet of the spiral separator is connected to the exhaust port of the evaporator 10, and its outlet is connected to the inlet of the porous media demister; the outlet of the porous media demister is connected to the gas phase inlet of the condenser 8; the gas phase outlet of the condenser 8 is connected to the second inlet of the ejector 2 via pipe D 7.

[0082] In some specific embodiments of this utility model, the condenser 8 can be a shell-and-tube heat exchanger, whose structure includes a shell and a plurality of heat exchange tubes disposed inside the shell, the heat exchange tubes being used for cooling water circulation. The mixture of water vapor and non-condensable gases, after liquid removal treatment, enters the shell from the condenser's gas phase inlet, flows through the shell side, and exchanges heat with the cooling water in the heat exchange tubes. The water vapor is condensed to form a second condensate, which is discharged from the shell's liquid phase outlet through a pipe to the condensate tank 13. The remaining non-condensable gases enter the ejector 2 from the gas phase outlet through pipe D7. This embodiment only applies the shell-and-tube heat exchanger and does not modify its structure.

[0083] The gaseous mixture generated during the waste liquid evaporation process mainly includes saturated water vapor, entrained droplets / droplets, and non-condensable gases. The vacuum negative pressure system continuously removes non-condensable gases, disrupting the gas-liquid phase equilibrium within the evaporation vessel 10, allowing water to continue evaporating at low temperatures. The gas-liquid separation system achieves near-zero escape of liquid pollutants through gas-liquid separation and condensation processes; residual non-condensable gases are dissolved and buffered in a buffer tank before being discharged in compliance with standards.

[0084] During operation, the waste liquid in the evaporator 10 evaporates and crystallizes under a vacuum of -99 kPa using low-pressure steam as a heat source, generating evaporation waste gas containing saturated water vapor, droplets, and non-condensable gases (such as air, CO2, etc.). This evaporation waste gas first enters a spiral separator to achieve centrifugal separation of large-diameter droplets, which are then returned to the evaporator 10. The dehydrated gas phase undergoes deep purification by a porous media demister to remove micron-sized droplets before entering the condenser 8. In the condenser 8, water vapor is condensed into liquid secondary condensate by cooling water and recovered to the condensate tank 13. Residual non-condensable gases are transported to the ejector 2 via pipe D 7. The ejector 2 uses a high-speed water flow drawn by a centrifugal pump 3 to eject the non-condensable gases, forming a gas-liquid two-phase flow that is sprayed into the buffer tank 4 for temporary storage. The vacuum pump 5 continuously draws gas from the gas phase space above the buffer tank 4 to maintain a high vacuum in the system.

[0085] This design employs a three-stage treatment process—graded gas-liquid separation, condensation, and gas ejection—to ensure efficient recovery of liquid components from evaporation waste gas. Non-condensable gases are discharged in trace amounts after passing through buffer tank 4, completely resolving the secondary pollution problem of traditional equipment.

[0086] Example 2

[0087] The residual temperature of the condensate formed after low-pressure steam heat exchange generally still exceeds 80°C. Direct discharge not only pollutes the environment but also wastes energy. Therefore, to improve the resource recovery rate of this equipment, Example 2, based on Example 1, also includes a waste heat recovery system. This system fully utilizes the waste heat of the steam condensate to preheat the raw liquid to above 40°C. The steam condensate is discharged after its residual temperature drops below 50°C, improving evaporation efficiency while achieving energy conservation and emission reduction, and preventing secondary thermal pollution to the environment.

[0088] Specifically, the waste heat recovery system includes a waste heat exchanger, which comprises a shell and several waste heat exchange tubes disposed inside the shell. In the first embodiment described above, the first condensate formed after low-pressure steam heat exchange is temporarily stored in a buffer tank. Therefore, in this second embodiment, the condensate in the buffer tank can be extracted through a pipeline and transported to the shell of the waste heat exchanger as a high-temperature medium. The waste liquid to be introduced into the evaporator flows through the tube side of the waste heat exchange tubes, serving as a preheating medium. The condensate, as a high-temperature medium above 80°C, preheats the waste liquid to above 40°C, ensuring that the waste liquid to be evaporated and crystallized receives a higher initial temperature, reducing energy consumption during subsequent evaporation and crystallization. The structure of the waste heat exchanger in this embodiment is the same as that of the condenser 8 in embodiment 1.

[0089] Example 3

[0090] To improve the automation level of the equipment, Embodiment 3, based on Embodiment 1, further configures an intelligent control system to achieve fully automated operation through multi-sensor collaboration and programmed logic. The equipment is equipped with the following control elements at key nodes:

[0091] An infrared sensor, preferably OPT-301, is installed at the viewing window 15 on the side wall of the evaporator 10 to monitor the phase change state and crystallinity of the material in real time; an ultrasonic sensor with a frequency of 20MHz is embedded in the inner wall to dynamically detect the liquid level and the concentration of the solid-liquid mixture.

[0092] The vapor outlet of condenser 8 is equipped with a negative pressure sensor 33, with a range of -100 to 0 kPa and an accuracy of ±0.5%FS.

[0093] Temperature sensors are installed on the steam inlet and steam outlet pipes of heat exchange jacket 16. The model can be PT100 platinum resistance thermometer.

[0094] Both the buffer water tank 4 and the condensate water tank 13 are equipped with level gauges, with optional magnetic float level gauges, and have 4-20mA signal output.

[0095] Pneumatic angle seat valves, DN50, are installed in inlet and outlet pipelines such as pipeline D7 and pipeline C, with position feedback switches.

[0096] Steam pipelines such as pipe F 17 are equipped with steam regulating valves to regulate the steam intake. An electric regulating valve with equal percentage characteristics and a CV value ≥ 120 can be selected.

[0097] The discharge port of the evaporator 10 is equipped with a pneumatic discharge valve, which is driven by a cylinder and has a response time of <1s.

[0098] The equipment is equipped with an intelligent control box 34, which integrates a PLC and an HMI touch screen. The PLC can be a Siemens S7-1200 series.

[0099] The automatic control process in this embodiment is implemented as follows:

[0100] Preheating Start-up:

[0101] When the negative pressure sensor detects that the system pressure is greater than -90 kPa, the PLC triggers the centrifugal pump 3 and vacuum pump 5 to start; the evaporator 10 automatically feeds liquid, the steam regulating valve 18 opens, and low-pressure steam enters the heat exchange jacket 16 to provide heat to heat the waste liquid in the evaporator 10. Under vacuum, the temperature of the waste liquid rises to about 25°C, and the waste liquid begins to evaporate, completing the preheating.

[0102] Evaporation and concentration process:

[0103] The evaporation temperature is set to 25℃. Low-grade steam continuously heats the waste liquid, causing the water to evaporate rapidly. The gaseous mixture, carrying liquid droplets, enters the gas-liquid separator 9, where the separated liquid droplets return to the evaporator 10. The mixture of water vapor and non-condensable gases enters the condenser 8, where heat exchange with the mixture is achieved through circulating cooling water. The water vapor liquefies upon cooling and enters the condensate tank 13, while the non-condensable gases enter the vacuum negative pressure system. Ultrasonic detection is used to check the solid content in the evaporator 10. Once the infrared sensor detects that the crystallization rate reaches 95%, a discharge preparation signal is triggered. The intelligent control box 34, with its built-in program, controls the speed of the reducer 12, the steam regulating valve, and the pneumatic control valve, among other actuators and valves, to begin discharging the crystals.

[0104] Crystallization discharge:

[0105] After one evaporation cycle is completed, the steam regulating valve is closed, the pneumatic discharge valve of the discharge pipe 31 is opened, the evaporator 10 is pressurized, and the crystals are forced from the discharge port into the crystal collection container.

[0106] Embodiment 3 of this utility model improves the operating efficiency of the equipment by integrating an automated control module, based on the hardware structure described in Embodiment 1. It should be noted that the technology of the sensors and actuators is mature.

[0107] Infrared sensors are industrial-grade standard infrared temperature measuring devices. They achieve non-contact temperature and crystallization state monitoring by receiving infrared energy radiated from the surface of materials. Those skilled in the art can directly purchase compatible models based on the device's window size and monitoring distance.

[0108] The ultrasonic sensor uses the pulse-echo ranging principle to detect liquid level and density of solid-liquid mixtures. It is a conventional liquid level monitoring solution for chemical containers. Its installation method is to embed and fix it in a standard threaded interface on the inner wall of the evaporator, which is a common assembly process for pressure vessels.

[0109] The pneumatic angle seat valve / pneumatic discharge valve is a two-position two-way valve driven by compressed air. The cylinder action is controlled by a solenoid valve. Its flange connection to the pipeline and position feedback switch are all basic technologies in the valve field.

[0110] Negative pressure sensors, temperature sensors, and level gauges are all standardized components in the field of industrial process control, and the market supply system is well-established.

[0111] The signal transmission and protocols involved are all feasible. The 4-20mA analog signals or RS485 digital signals output by each sensor are connected to the PLC analog input module through shielded cables; the actuators are driven by the PLC digital output module, and the control logic is implemented through ladder diagram programming.

[0112] Therefore, the sensor selection, installation method, signal transmission and control logic involved in this embodiment are all within the scope of existing technology. For specific implementation details, please refer to manuals such as "Industrial Automation Instrument Manual" and "PLC Programming and Application". These are technical means that can be directly implemented by those skilled in the art through standard technical manuals or common knowledge, and will not be elaborated here.

[0113] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this invention shall be determined by the claims.

Claims

1. A low-pressure steam reuse evaporation crystallization device, characterized in that, Includes a vacuum negative pressure system and an evaporation crystallization system; The vacuum negative pressure system includes an ejector (2), a centrifugal pump (3), a buffer tank (4), and a vacuum pump (5). The jet ejector (2) is provided with a first inlet, a second inlet and a first outlet; The first inlet is connected to the outlet of the centrifugal pump (3), the second inlet is connected to the exhaust port of the evaporation crystallization system through pipe D (7), and the first outlet is connected to the first inlet of the buffer water tank (4) through pipe A (11). The inlet of the centrifugal pump (3) is connected to the first outlet of the buffer tank (4) via pipe B (6); The inlet of the vacuum pump (5) is connected to the gas outlet of the buffer tank (4) through pipe C, and its outlet is connected to the external environment or connected to the gas buffer container through a gas pipe.

2. The low-pressure steam reuse evaporation crystallization equipment according to claim 1, characterized in that, The evaporation crystallization system includes an evaporation kettle (10) and a condensate tank (13). The evaporator (10) has a cylindrical structure and a heat exchange jacket (16) is fitted on its outer side. The evaporator (10) is provided with an exhaust port and a liquid inlet. The heat exchange jacket (16) forms a closed steam chamber with the outer wall of the evaporator (10). The heat exchange jacket (16) has a steam inlet and a steam outlet on its side wall. The steam inlet is connected to the steam generator through pipe F (17), and the steam outlet is connected to the condensate tank (13) through pipe E (19).

3. The low-pressure steam reuse evaporation crystallization equipment according to claim 2, characterized in that, The evaporation crystallization system also includes a scraping assembly and a driving assembly; The scraping assembly includes a stirring shaft (20) and a spiral scraper (21). The stirring shaft (20) is coaxially arranged with the evaporator (10), and its two ends are movably connected to the end sidewalls of the evaporator (10). The spiral scraper (21) is sleeved on the outside of the stirring shaft (20) in an equidistant spiral structure. Its outer edge contacts the inner wall of the evaporator (10), and its inner edge is connected to the stirring shaft (20) through the support column (25). The drive assembly is driven to the stirring shaft (20).

4. The low-pressure steam reuse evaporation crystallization equipment according to claim 3, characterized in that, The drive assembly includes a drive sprocket (27), a driven sprocket (28), a chain (29), and a drive motor (30). The drive motor (30) is located below one end of the evaporator (10); The drive sprocket (27) is mounted on the output shaft of the drive motor (30); The driven sprocket (28) is mounted on the end of the stirring shaft (20) on the same side as the driving sprocket (27); The chain (29) meshes with the driving sprocket (27) and the driven sprocket (28).

5. The low-pressure steam reuse evaporation crystallization equipment according to claim 2, characterized in that, The evaporator (10) has a discharge port on one end side wall, and a pneumatic discharge valve is installed at the discharge port.

6. The low-pressure steam reuse evaporation crystallization equipment according to claim 2, characterized in that, The evaporation crystallization equipment also includes a gas-liquid separation system; The gas-liquid separation system includes a spiral separator, a porous media demister and a condenser (8) connected in sequence. The inlet of the spiral separator is connected to the exhaust port of the evaporator (10); The gas phase outlet of the condenser (8) is connected to the second inlet of the ejector (2) through the pipe D (7).

7. The low-pressure steam reuse evaporation crystallization equipment according to claim 2, characterized in that, The inner wall of the evaporator (10) is coated with an anti-stick coating.

8. The low-pressure steam reuse evaporation crystallization equipment according to claim 2, characterized in that, The evaporation crystallization equipment also includes a waste heat recovery system; The waste heat recovery system includes a waste heat exchanger, which includes a shell and a plurality of waste heat exchange tubes disposed inside the shell. The working fluid inlet of the outer shell is connected to the outlet of the condensate tank (13); The inlet of the waste heat exchange tube is connected to the waste liquid storage tank, and its outlet is connected to the inlet of the evaporator (10).

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