Efficient MVR (mechanical vapor recompression) evaporation system applied to high-salinity wastewater treatment

Abstract

The invention relates to the technical field of wastewater treatment equipment, and particularly provides an efficient MVR evaporation system applied to high-salinity wastewater treatment.The efficient MVR evaporation system comprises a falling-film evaporator, a separator, a compressor and a centrifugal machine, the falling-film evaporator comprises a distributor, a driving device, a scraper, a steam cavity and a falling-film pipe, and the falling-film pipe penetrates through the steam cavity in the vertical direction; the distributor is arranged above the falling film tube and used for distributing feeding high-salinity wastewater, the scraper is arranged on the inner side of the falling film tube and is of a spiral strip-shaped structure, the outer side of a spiral line of the scraper is attached to the inner wall of the falling film tube, and the driving device is used for driving the scraper to reciprocate in the vertical direction. The spiral scraper is matched with the driving device to change the flowing trend of fluid in the falling film tube, and meanwhile, scale can be cut and removed through vertical movement of the spiral scraper, so that accumulation and growth of crystals are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment equipment, and particularly to an efficient MVR evaporation system applied to the treatment of high-salt wastewater. Background Art

[0002] The MVR evaporation system is an efficient and energy-saving evaporation technology, which is widely used in the fields of chemical industry, pharmaceuticals, food processing, wastewater treatment, etc. Its core principle is to utilize the secondary steam generated during the evaporation process. After being compressed by a positive gas compressor, its temperature and pressure are increased, and it is reused as a heat source to heat the material, thereby realizing the recycling of thermal energy.

[0003] However, in practical applications, the MVR evaporation system faces some challenges. For example, when processing certain high-concentration materials, due to the difference in the uniformity of liquid material distribution, the liquid material in the tube pass of its liquid distributor is extremely prone to drying and crystallization precipitation, which will cause the heat exchanger to become blocked. Therefore, it is necessary to frequently stop the MVR evaporator for cleaning, seriously affecting the production efficiency.

[0004] Based on this, there is an urgent need for an efficient MVR evaporation system that can be applied to high-salt wastewater and can reduce the probability of blockage. Summary of the Invention

[0005] In view of this, the present invention proposes an efficient MVR evaporation system applied to the treatment of high-salt wastewater.

[0006] The technical solution of the present invention is realized as follows: The present invention provides an efficient MVR evaporation system applied to the treatment of high-salt wastewater, which includes: a falling film evaporator, a separator, a compressor, and a centrifuge. The high-salt wastewater is fed from the top of the falling film evaporator. The bottom side of the falling film evaporator is communicated with the feed port of the separator. The bottom discharge port of the separator and the bottom discharge port of the falling film evaporator are both communicated with the centrifuge. The steam outlet at the top of the separator is communicated with the intake port of the compressor. The outlet of the compressor is communicated with the intake port of the falling film evaporator. The falling film evaporator includes a distributor, a driving device, a scraper, a steam chamber, and falling film tubes. The falling film tubes penetrate the steam chamber in the vertical direction. The distributor is arranged above the falling film tubes and is used to distribute the fed high-salt wastewater. The scraper is arranged inside the falling film tubes. The scraper is a spiral strip structure, and the outer side of its spiral line fits with the inner wall of the falling film tubes. The driving device is used to drive the scraper to reciprocate in the vertical direction.

[0007] In some embodiments, there are two driving devices, which are respectively arranged at the upper and lower ends of the scraper.

[0008] In some embodiments, the driving device includes an external driver and a magnetic ring. The external driver is fixedly arranged on the outer surface of the falling-film evaporator. The magnetic ring is coaxially and slidably arranged above the steam chamber in the vertical direction. A plurality of scraping devices are fixedly connected to the magnetic ring. The external driver can magnetically drive the magnetic ring to reciprocate up and down inside the falling-film evaporator.

[0009] In some embodiments, the external driver includes a linear module and a magnet. The magnet is fixed at the driving end of the linear module. The linear module can drive the magnet to reciprocate synchronously in the vertical direction. The magnet is magnetically coupled with the magnetic ring.

[0010] The magnet of the external driver is coupled with the magnetic ring through a magnetic field (gap ≤ 2 mm), realizing non-contact transmission of power and solving the problems of easy leakage and poor corrosion resistance of traditional mechanical seals.

[0011] Sealing guarantee: A laser-welded stainless-steel isolation sleeve (thickness 1.5 mm) is used between the magnetic ring and the falling-film tube, with a pressure resistance ≥ 2.5 MPa, ensuring complete isolation between the steam chamber and the driving component;

[0012] Motion precision control: The linear module drives the magnet to move synchronously (positioning precision ±0.1 mm), and the real-time position is fed back through a Hall sensor to avoid jamming.

[0013] In some embodiments, the scraping device is evenly divided into an upper section, a middle section, and a lower section from top to bottom along the spiral axis direction, and the pitches of the upper section, the middle section, and the lower section decrease in sequence.

[0014] In some embodiments, the pitch of the upper section is 35 - 45 mm, the pitch of the middle section is 25 - 35 mm, and the pitch of the lower section is 15 - 25 mm.

[0015] The scraping device is divided into an upper section (pitch 40 - 50 mm), a middle section (25 - 35 mm), and a lower section (15 - 20 mm), and is optimized according to the scaling characteristics of different pipe sections:

[0016] Large pitch in the upper section: Enhance the turbulence in the inlet area (Reynolds number Re > 8000) to prevent initial crystal attachment;

[0017] Small pitch in the lower section: Increase the wall shear force (> 8 Pa) to remove the dense scale layer in the high-concentration area;

[0018] Gradual change of pitch for transition: Avoid local dead zones caused by flow separation and maintain the flow velocity uniformity in the whole pipe section.

[0019] In some embodiments, the cross-section of the scraping device is semi-circular, and the side where the diameter is located is attached to the inner wall of the falling-film tube.

[0020] In some embodiments, in the cross-section of the scraping device, the flow-facing side of the semi-circle is acute, and an arc-shaped groove is provided on the flow-back side of the semi-circle.

[0021] In some embodiments, a tungsten carbide coating is cladded on the semicircular flow-facing side surface.

[0022] In some embodiments, an alumina ceramic film is attached to the inner wall surface of the arc-shaped groove on the semicircular flow-back side.

[0023] A tungsten carbide layer with a thickness of 50 μm is formed on the edge surface by laser cladding process, which improves the wear resistance life and can withstand the long-term scouring of high-salt crystallization.

[0024] Porous Al2O3 ceramic film is generated in the groove by micro-arc oxidation, which reduces the surface energy and inhibits the secondary deposition of salts in the groove.

[0025] The scraper moves periodically up and down along the axial direction of the falling film tube driven by the driving device. Its spiral edge is closely attached to the inner wall of the falling film tube. The dynamic anti-blocking is achieved through the following synergistic effects:

[0026] Mechanical scraping: The acute angle design of the spiral edge (30° edge angle on the flow-facing side) generates local shear stress on hard scales (such as CaSO4 and NaCl crystals), breaking and peeling off the formed scale layer;

[0027] Fluid disturbance: When the scraper moves, the spiral structure induces the fluid to form a swirling flow, increasing the tangential velocity, destroying the boundary layer and inhibiting the deposition of new scales;

[0028] Self-cleaning effect: Scraping hard scales during the descending stage and using fluid flushing to carry out the broken scales out of the system during the ascending stage to form a closed-loop cleaning.

[0029] The present invention has the following beneficial effects compared with the prior art:

[0030] The present invention uses a spiral scraper in cooperation with a driving device to change the fluid flow trend inside the falling film tube. At the same time, the cutting and removal of accumulated scales can be realized through the up and down movement of the spiral scraper, avoiding the growth of crystal accumulation, effectively extending the stable operation period of the MVR evaporation system, improving the efficiency of wastewater evaporation treatment, and having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is a connection schematic diagram of the high-efficiency MVR evaporation system of the present invention;

[0033] Figure 2 It is a partial enlarged view of the falling film evaporator in the high-efficiency MVR evaporation system of the present invention;

[0034] Figure 3 It is the main sectional view of the scraper in the high-efficiency MVR evaporation system of the present invention;

[0035] Figure 4 It is the sectional view of the scraper in the high-efficiency MVR evaporation system of the present invention.

[0036] In the figure: 1 - falling film evaporator, 2 - separator, 3 - compressor, 4 - centrifuge, 11 - distributor, 12 - drive device, 13 - scraper, 14 - steam chamber, 15 - falling film tube, 121 - external driver, 122 - magnetic ring, 1211 - linear module, 1212 - magnet, 131 - upstream side, 132 - downstream side. Detailed implementation manners

[0037] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0039] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application.

[0040] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the embodiments of the present invention belong. If the definitions stated in this part are contrary to or inconsistent with the definitions stated in the patents, patent applications, published patent applications and other publications incorporated herein by reference, the definitions listed in this part shall prevail over the definitions incorporated herein by reference.

[0041] Unless otherwise specified, the methods used in the following embodiments are all conventional methods. The materials, reagents, and instruments used, unless otherwise specified, are all conventional materials, reagents, and instruments in the art, and those skilled in the art can obtain them through commercial channels.

[0042] As Figure 1 shown, in combination with Figures 2 - 4 , the efficient MVR evaporation system of the present invention applied to the treatment of high-salt wastewater includes: a falling-film evaporator 1, a separator 2, a compressor 3, and a centrifuge 4. The high-salt wastewater is fed from the top of the falling-film evaporator 1. The bottom side of the falling-film evaporator 1 is communicated with the feed port of the separator 2. The bottom discharge port of the separator 2 and the bottom discharge port of the falling-film evaporator 1 are both communicated with the centrifuge 4. The steam outlet at the top of the separator 2 is communicated with the intake port of the compressor 3. The outlet of the compressor 3 is communicated with the intake port of the falling-film evaporator 1. It is characterized in that the falling-film evaporator 1 includes a distributor 11, a driving device 12, a scraper 13, a steam chamber 14, and falling-film tubes 15. The falling-film tubes 15 penetrate the steam chamber 14 in the vertical direction. The distributor 11 is arranged above the falling-film tubes 15. The distributor 15 is used to distribute the fed high-salt wastewater. The scraper 13 is arranged inside the falling-film tubes 15. The scraper 13 is in a spiral strip structure, and the outer side of its spiral line fits the inner wall of the falling-film tubes 15. The driving device 12 is used to drive the scraper 13 to reciprocate in the vertical direction.

[0043] In the above embodiments, the high-salt wastewater is pumped from the waste liquid pool into the distributor 11. After being distributed by the distributor 11, the waste liquid flows between the falling-film tubes 15 and finally flows downward along the inner wall of the falling-film tubes 15, thus forming a liquid film. During the downward flow, the spiral scraper 13 guides the liquid flow, thereby prolonging the time of heat exchange between the liquid flow in the falling-film tubes 15 and the steam in the steam chamber 14, improving the energy utilization rate. At the same time, according to requirements, the driving device 12 can be selected to drive the scraper 13 to move up and down. The spiral structure can scrape and shear the inner wall of the falling-film tubes 15 to avoid crystal attachment, thus keeping the falling-film tubes 15 unobstructed. The gas-liquid mixture after evaporation treatment enters the separator 2 for separation. The steam enters the compressor 3 again for pressurized recycling. The compressor 3 is also communicated with a steam generating device to supplement steam. The liquid after separation enters the centrifuge 4 for centrifugal separation to obtain solid salt and wastewater. The waste liquid at the bottom of the falling-film evaporator 1 can also be directly discharged into the centrifuge 4 for centrifugal treatment after reaching the corresponding concentration.

[0044] The waste liquid fed into the distributor 11 can be preheated one or more times to avoid violent temperature rise in the falling-film tubes 15.

[0045] In some embodiments, two driving devices 12 are provided and are respectively arranged at the upper and lower ends of the scraper 13.

[0046] In the above embodiments, the driving device 12 is used to drive the scraper 13 to move up and down. In order to achieve a more stable driving effect, corresponding driving devices 12 can be provided at both the upper and lower ends of the scraper 13 at the same time.

[0047] In some embodiments, the driving device 12 includes an external driver 121 and a magnetic ring 122. The external driver 121 is fixedly arranged on the outer surface of the falling film evaporator 1, and the magnetic ring 122 is coaxially and slidably arranged above the steam chamber 14 in the vertical direction. A plurality of scrapers 13 are fixedly connected to the magnetic ring 122, and the external driver 121 can magnetically drive the magnetic ring 122 to reciprocate up and down inside the falling film evaporator 1.

[0048] In the above embodiments, the magnetic ring 122 is used for magnetic coupling with the external driver 121. A structure for guiding and supporting the magnetic ring is further arranged on the inner wall of the falling film evaporator 1. For example, a polytetrafluoroethylene support rod is used, as Figure 2 shown, the magnetic ring 122 is limited, supported and guided by the support rod. The magnetic ring 122 is also used to fix a plurality of scrapers 13. For example, a connecting grid is arranged in the middle of the magnetic ring 122, and the scrapers 13 are connected or supported by the grid. The grid will not block the liquid flow flowing down from the distributor 11 and the liquid flow flowing out of the falling film tube 15. Under the magnetic drive of the external driver 121, the magnetic ring 122 can be driven up and down in a non-contact manner, so as to drive the scraper 13 to scrape up and down.

[0049] In some embodiments, the external driver 121 includes a linear module 1211 and a magnet 1212. The magnet 1212 is fixed at the driving end of the linear module 1211, and the linear module 1211 can drive the magnet 1212 to reciprocate synchronously in the vertical direction. The magnet 1212 is magnetically coupled with the magnetic ring 122.

[0050] In the above embodiments, the linear module 1211 is used to drive the magnet 1212 to move up and down, so as to be magnetically coupled with the internal magnetic ring 122 and drive the magnetic ring 122 to move up and down. It should be understood that the outer shell of the falling film evaporator 1 in the magnetic ring moving area should be made of low magnetic permeability materials, such as austenitic stainless steel, titanium alloy, ceramic material, fiber composite material, etc.

[0051] In some embodiments, the scraper 13 is evenly divided into an upper section, a middle section and a lower section from top to bottom along the spiral axis direction, and the pitches of the upper section, the middle section and the lower section decrease in turn.

[0052] In the above embodiments, a large pitch design is adopted in the upper section, which can enhance the turbulence degree in the inlet area of the falling film tube and prevent the attachment of initial crystallization; a small pitch is used in the lower section, which can increase the wall shear force and remove the dense scale layer in the high-concentration area; the pitch can adopt a gradual transition to avoid local dead zones caused by wall flow separation and maintain the flow velocity uniformity in the whole pipe section.

[0053] In some embodiments, the pitch of the upper section is 35 - 45 mm, the pitch of the middle section is 25 - 35 mm, and the pitch of the lower section is 15 - 25 mm.

[0054] In some embodiments, the cross-section of the scraper 13 is semi-circular, and the side where its diameter is located fits the inner wall of the falling film tube.

[0055] In some embodiments, in the cross-section of the scraper 13, the flow-facing side 131 of the semi-circle is acute, and an arc-shaped groove is provided on the flow-back side 132 of the semi-circle.

[0056] In the above embodiments, the acute angle design of the spiral edge (30° edge angle on the flow-facing side) generates local shear stress (>50 MPa) on hard scales (such as CaSO4 and NaCl crystals), breaking and peeling off the formed scale layer; when the scraper moves, the spiral structure induces the fluid to form a swirling flow, destroying the boundary layer and inhibiting the deposition of new scales; the hard scales are scraped during the descending stage, and the broken scales are carried out of the system by fluid flushing during the ascending stage, forming a closed-loop cleaning. When the scraper moves, the groove structure on the flow-back side will induce a stable reverse secondary eddy current. This eddy current can: destroy the boundary layer, form a velocity gradient between the main fluid flow and the pipe wall, and increase the turbulent kinetic energy near the wall surface, inhibiting the uniform deposition of salt crystallization.

[0057] In some embodiments, a tungsten carbide coating is cladded on the surface of the flow-facing side 131 of the semi-circle.

[0058] A tungsten carbide layer with a thickness of 50 μm is formed on the edge surface by laser cladding technology, and the wear-resistant life is increased by more than 5 times, which can withstand the long-term erosion of high-salt crystallization.

[0059] In some embodiments, an alumina ceramic film is attached to the inner wall surface of the arc-shaped groove on the flow-back side 132 of the semi-circle.

[0060] A porous Al2O3 ceramic film is generated in the groove by micro-arc oxidation to reduce the surface energy and inhibit the secondary deposition of salts in the groove.

[0061] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An efficient MVR evaporation system for high-salinity wastewater treatment, comprising: A falling film evaporator (1), a separator (2), a compressor (3) and a centrifuge (4); high-salt wastewater is fed from the top of the falling film evaporator (1); the bottom side of the falling film evaporator (1) is connected to the feed port of the separator (2); the bottom discharge port of the separator (2) and the bottom discharge port of the falling film evaporator (1) are both connected to the centrifuge (4); the steam outlet at the top of the separator (2) is connected to the air inlet of the compressor (3); the air outlet of the compressor (3) is connected to the air inlet of the falling film evaporator (1); and the falling film evaporator (1) is characterized in that The invention comprises a distributor (11), a driving device (12), a scraper (13), a steam chamber (14) and a falling film tube (15). The falling film tube (15) penetrates the steam chamber (14) in a vertical direction. The distributor (11) is arranged above the falling film tube (15). The distributor (15) is used to distribute the high-salt wastewater as feed. The scraper (13) is arranged on the inner side of the falling film tube (15). The scraper (13) is a spiral strip structure. The outer side of the spiral line is in contact with the inner wall of the falling film tube (15). The driving device (12) is used to drive the scraper (13) to reciprocate in the vertical direction.

2. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 1, characterized in that: The driving devices (12) are provided with two, which are respectively arranged at the upper and lower ends of the scraper (13).

3. The high-efficiency MVR evaporation system for high-salt wastewater treatment according to claim 1, characterized in that: The driving device (12) comprises an external driver (121) and a magnetic ring (122); the external driver (121) is fixedly arranged on the outer surface of the falling film evaporator (1); the magnetic ring (122) is coaxially slidably arranged above the steam chamber (14) in a vertical direction; a plurality of scrapers (13) are fixedly connected to the magnetic ring (122); and the external driver (121) can magnetically drive the magnetic ring (122) to reciprocate up and down on the inner side of the falling film evaporator (1).

4. The high-efficiency MVR evaporation system for high-salt wastewater treatment according to claim 3 is characterized in that: The external driver (121) comprises a linear module (1211) and a magnet (1212); the magnet (1212) is fixed to a driving end of the linear module (1211); the linear module (1211) can drive the magnet (1212) to synchronously reciprocate in a vertical direction; the magnet (1212) is magnetically coupled to the magnetic ring (122).

5. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 1, characterized in that: The scraper (13) is evenly divided into an upper section, a middle section and a lower section from top to bottom along the spiral axis direction, and the pitches of the upper section, the middle section and the lower section decrease in sequence.

6. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 5, characterized in that: The upper thread pitch is 35-45mm, the middle thread pitch is 25-35mm, and the lower thread pitch is 15-25mm.

7. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 1, characterized in that: The scraper (13) has a semicircular cross section, and one side of the scraper (13) where the diameter is located is in contact with the inner wall of the falling film tube.

8. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 7, characterized in that: In the cross section of the scraper (13), the semicircular upstream side (131) is acute-angled, and the semicircular downstream side (132) is provided with an arc-shaped groove.

9. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 8, characterized in that: The surface of the semicircular upstream side (131) is clad with a tungsten carbide coating.

10. The high-efficiency MVR evaporation system for high-salinity wastewater treatment according to claim 8, characterized in that: An alumina ceramic film is attached to the inner wall surface of the arc-shaped groove on the semicircular backflow side (132).

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