Anti-fouling MVR evaporator

Abstract

The present application relates to wastewater treatment equipment technical field, specifically proposes a kind of scale prevention type MVR evaporator, it includes: falling film evaporator, separator, compressor and centrifuge, the falling film evaporator includes distributor, steam cavity and falling film tube, falling film tube is along vertical direction and passes through steam cavity, distributor is set in the upper of falling film tube, distributor is used to distribute to incoming material high-salt wastewater, falling film tube inner surface is equipped with gradual change layer, the surface of gradual change layer gradually increases from top to bottom contact angle, the present application is synergistically optimized by four-zone gradient wetting surface design and partition preparation process, realizes the technical effect that the scaling rate is reduced in high-salt wastewater evaporation process, heat transfer efficiency is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment equipment, and particularly relates to a scale-prevention type MVR evaporator. BACKGROUND

[0002] As a core equipment for high-salinity wastewater treatment, the scale-prevention technology of the MVR evaporator has always been a difficulty in the industry. In the prior art, a scale inhibitor is generally added to inhibit salt analysis. This scheme needs to continuously add chemical agents, which has environmental protection risks and may affect the properties of the wastewater in long-term use. Traditional mechanical cleaning needs to be maintained during shutdown, which not only is difficult to operate, but also greatly reduces the wastewater treatment efficiency.

[0003] The existing scheme has a contradiction among scale-prevention effect, energy efficiency and environmental protection, and there is an urgent need for a passive scale-prevention type MVR evaporator which does not need chemical intervention and can continuously inhibit scale formation. SUMMARY

[0004] Therefore, the present application provides a scale-prevention type MVR evaporator.

[0005] The technical scheme of the present application is implemented as follows: The present application provides a scale-prevention type MVR evaporator, which comprises a falling film evaporator, a separator, a compressor and a centrifuge. High-salinity wastewater is fed from the top of the falling film evaporator. The side surface at the bottom of the falling film evaporator is in communication with the feed inlet of the separator. The bottom discharge outlet of the separator and the bottom discharge outlet of the falling film evaporator are both in communication with the centrifuge. The steam outlet at the top of the separator is in communication with the air inlet of the compressor. The air outlet of the compressor is in communication with the air inlet of the falling film evaporator. The falling film evaporator comprises a distributor, a steam cavity and a falling film tube. The falling film tube penetrates the steam cavity in the vertical direction. The distributor is arranged above the falling film tube. The distributor is used for distributing the high-salinity wastewater. The inner surface of the falling film tube is provided with a gradient layer. The contact angle of the surface of the gradient layer gradually increases from top to bottom.

[0006] In some embodiments, the gradient layer comprises, in sequence from top to bottom, a main hydrophilic layer, a transition hydrophilic layer, a transition hydrophobic layer and a main hydrophobic layer. The contact angle of the main hydrophilic layer is less than 10 degrees. The contact angle of the transition hydrophilic layer is 10-30 degrees. The contact angle of the transition hydrophobic layer is 60-90 degrees. The contact angle of the main hydrophobic layer is greater than 110 degrees. The main hydrophilic layer accounts for 20-30% of the length of the gradient layer. The transition hydrophilic layer accounts for 25-35% of the length of the gradient layer. The transition hydrophobic layer accounts for 20-30% of the length of the gradient layer. The main hydrophobic layer accounts for 15-25% of the length of the gradient layer.

[0007] In some embodiments, the preparation method of the main hydrophilic layer comprises: immersing the main hydrophilic layer region of the falling film tube made of titanium into an electrolyte and connecting the anode of the power supply to the falling film tube, immersing a carbon rod into the electrolyte and connecting the cathode of the power supply to the carbon rod, starting the pulse power supply, and after electrolytic treatment, cleaning and drying to obtain the main hydrophilic layer. The electrolyte contains 10 g / L of Na2SiO3 and 2 g / L of KOH.

[0008] In some embodiments, the electrolytic treatment conditions include: temperature of 25-30℃, 400V pulse direct current, frequency of 1000Hz, and electrolytic treatment for 10-20min.

[0009] When the electrolysis time is in the range of 10-20min, the uniformity of the nano-porous structure (SEM detection porosity deviation <5%) can meet the anti-fouling requirements.

[0010] In some embodiments, the preparation method of the transition hydrophilic layer comprises: using a galvanometer scanning system to process a parallel micro-groove array in the transition hydrophilic layer region, so that the direction of the micro-groove is at an angle of 45° with the fluid flow direction, and after treatment, cleaning and drying.

[0011] In some embodiments, the processing laser wavelength is 1064nm, the power is 200W, the scanning speed is 50mm / s, the line spacing is 20μm, the parallel micro-groove width is 20μm, and the depth is 5μm.

[0012] In some embodiments, the preparation method of the transition hydrophobic layer comprises: first using laser to process a micro-dimple array on the surface of the transition hydrophobic layer region, then spraying perfluorooctyltriethoxysilane on the surface of the transition hydrophobic layer region, and then heating to 120℃ for baking treatment for 20-40min.

[0013] In some embodiments, the laser power is 50W, the diameter of the micro-dimple is 5-10μm, and the depth is 2μm.

[0014] In some embodiments, the preparation method of the main hydrophobic layer comprises: exposing the main hydrophobic layer region to a CVD reaction chamber and aligning the gas nozzle, heating to 250℃, then introducing hexamethyldisilazane and argon carrier gas, depositing for 2h, and then vacuum annealing at 300℃ for 1h.

[0015] In some embodiments, the gas flow of hexamethyldisilazane is 20sccm, and the argon flow is 50sccm.

[0016] In the present application, the main hydrophilic layer (θ < 10°) spreads the liquid film quickly through the nanoporous structure, forming a continuous liquid film with a thickness of <0.1mm, avoiding the formation of hard scale such as CaSO4 and CaCO3 caused by local dryness. The microgroove structure (width 20μm) of the transition hydrophilic layer (θ = 10°-30°) induces turbulent flow, destroying the directional growth of crystal nucleus. The micro-pit (diameter 5-10μm) of the transition hydrophobic layer (θ = 60°-90°) forms a gas film through the Cassie-Baxter effect, reducing the solid-liquid contact area. The nanopillar array (height 500nm) of the main hydrophobic layer (θ > 110°) induces droplet bouncing effect, stripping the soft scale at the initial stage.

[0017] The main hydrophilic zone ultra-thin liquid film reduces the thermal resistance, the transition zone microgroove enhances the turbulent flow, and the main hydrophobic zone maintains stable heat transfer by inhibiting excessive boiling.

[0018] First, the main hydrophilic layer is treated by high-energy PEO, then the transition zone is laser processed, and finally low-temperature fluorination spraying and CVD deposition are performed, avoiding the damage of high-temperature process to the treated area.

[0019] The matching of laser power (200W) and scanning speed (50mm / s) ensures the consistency of microgroove depth (5±0.5μm), and the balance of CVD deposition temperature (250℃) and precursor flow rate (20sccm HMDSN) realizes the vertical growth of nanopillars.

[0020] The present application has the following beneficial effects compared with the prior art:

[0021] The present application realizes the significant effect of significantly reducing the scaling rate and significantly improving the heat transfer efficiency in the high-salinity wastewater evaporation process through the synergistic optimization of four-zone gradient wetting surface design and partitioned preparation process. It has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Fig. 1 is the connection schematic diagram of the anti-scaling MVR evaporation system of the present application;

[0024] Fig. 2 is the longitudinal sectional view of the falling film tube in the anti-scaling MVR evaporation system of the present application.

[0025] In the figure: 1 - falling film evaporator, 2 - separator, 3 - compressor, 4 - centrifuge, 11 - distributor, 12 - steam chamber, 13 - falling film tube, 14 - gradient layer, 141 - main hydrophilic layer, 142 - transition hydrophilic layer, 143 - transition hydrophobic layer, 144 - main hydrophobic layer. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] It should be noted that when an element is referred to as being "fixed" 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.

[0028] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present application belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with the definitions set forth in the patents, patent applications, published patent applications, and other publications that are herein incorporated by reference, the definitions set forth in this section are preferred.

[0030] The methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents and instruments used are conventional materials, reagents and instruments in the art unless otherwise specified, and can be obtained by commercial channels by those skilled in the art.

[0031] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0032] like Figs. 1-2 As shown, the scale-resistant MVR evaporator of the present invention includes: 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 inlet of the separator 2. The bottom outlet of the separator 2 and the bottom outlet 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. The falling film evaporator 1 is characterized in that it includes a distributor 11, a steam chamber 12, and a falling film tube 13. The falling film tube 13 penetrates the steam chamber 12 vertically. The distributor 11 is disposed above the falling film tube 13 and is used to distribute the fed high-salt wastewater. The inner surface of the falling film tube 13 is provided with a gradient layer 14, and the contact angle of the surface of the gradient layer 14 gradually increases from top to bottom.

[0033] The gradient layer 14 comprises, from top to bottom, a main hydrophilic layer 141, a transitional hydrophilic layer 142, a transitional hydrophobic layer 143, and a main hydrophobic layer 144. The contact angle θ of the main hydrophilic layer 141 is less than 10°, the contact angle θ of the transitional hydrophilic layer 142 is 10°-30°, the contact angle θ of the transitional hydrophobic layer 143 is 60°-90°, and the contact angle θ of the main hydrophobic layer 144 is greater than 110°. The main hydrophilic layer 141 occupies 20-30% of the length of the gradient layer 14, the transitional hydrophilic layer 142 occupies 25-35% of the length of the gradient layer 14, the transitional hydrophobic layer 143 occupies 20-30% of the length of the gradient layer 14, and the main hydrophobic layer 144 occupies 15-25% of the length of the gradient layer 14.

[0034] Example 1

[0035] This embodiment provides a solution for a four-zone gradient wettability falling film tube.

[0036] 1. Materials and Equipment

[0037] Substrate: TA2 industrial pure titanium tube (Φ25x6000mm, wall thickness 2mm)

[0038] Equipment: PEO power supply (400V / 20A), fiber laser processing machine (1064nm), CVD tube furnace

[0039] 2. Preparation steps

[0040] Step 1: Main hydrophilic layer treatment

[0041] The mask covers the non-treatment area (25% of the length of the main hydrophilic layer).

[0042] Electrolyte: 10g / L Na2SiO3+2g / L KOH, constant temperature at 25℃.

[0043] PEO treatment: 400V pulse direct current, frequency 1000Hz, time 15min.

[0044] Ultrasonic cleaning (deionized water, 5min), nitrogen blowing dry.

[0045] Step 2: Transition hydrophilic layer treatment

[0046] Laser parameters: 1064nm, 200W, 50mm / s, line spacing 20μm.

[0047] Process 45° diagonal microgrooves (width 20μm, depth 5μm), length ratio 30%.

[0048] Step 3: Transition hydrophobic layer treatment

[0049] Laser processing micro-pits (50W, diameter 5-10μm, depth 2μm), length ratio 25%.

[0050] Spray 5wt% perfluorooctyltriethoxysilane (spray pressure 0.3MPa).

[0051] Bake at 120℃ for 30min to form a fluorinated coating.

[0052] Step 4: Main hydrophobic layer treatment

[0053] CVD deposition: 250℃, HMDSN 20sccm+Ar 50sccm, time 2h.

[0054] Vacuum annealing: 300℃, 1h.

[0055] 3. Performance test

[0056] Fouling test: treat high-salinity wastewater, wastewater Cl - concentration 18%, Ca 2+5000mg / L, flow rate 1.5m / s, temperature 80℃, continuous running for 72 hours. Fouling rate was tested by weighing method, reaching 2.0g / m 2 ·h.

[0057] Fouling thickness: SEM showed that the fouling layer in the main hydrophobic zone was only 38μm, and the traditional pipe was 320μm.

[0058] Fouling morphology: XRD analysis showed that the fouling layer was loose CaSO4·2H2O.

[0059] Heat transfer test: under the same working conditions, the heat transfer coefficient K was measured to be 2870W / m 2 ·℃.

[0060] Example 2

[0061] The difference between this example and Example 1 is that the length ratio of the main hydrophilic layer, the transition hydrophilic layer, the transition hydrophobic layer and the main hydrophobic layer is 20%, 30%, 25% and 25% respectively.

[0062] The fouling rate of this example is 2.1g / m 2 ·h, and the heat transfer coefficient is 2850W / m 2 ·℃.

[0063] Example 3

[0064] The difference between this example and Example 1 is that the length ratio of the main hydrophilic layer, the transition hydrophilic layer, the transition hydrophobic layer and the main hydrophobic layer is 30%, 35%, 20% and 15% respectively.

[0065] The fouling rate of this example is 2.5g / m 2 ·h, and the heat transfer coefficient is 2700W / m 2 ·℃.

[0066] Example 4

[0067] The difference between this example and Example 1 is that the length ratio of the main hydrophilic layer, the transition hydrophilic layer, the transition hydrophobic layer and the main hydrophobic layer is 25%, 30%, 22% and 23% respectively.

[0068] The fouling rate of this example is 2.3g / m 2 ·h, and the heat transfer coefficient is 2800W / m 2 ·℃.

[0069] Comparative Example 1

[0070] This comparative example is based on Example 1, and the whole pipe PEO treatment is used, and the inner wall of the whole pipe is treated according to the treatment method of the main hydrophilic layer in Example 1.

[0071] The fouling rate of this comparative example is 8.7g / m2 • h, heat transfer coefficient 2100 W / m 2 • C.

[0072] Comparative Example 2

[0073] This comparative example is based on Example 1, using full tube CVD treatment, the inner wall of the full tube is treated according to the treatment method of the main hydrophobic layer in Example 1.

[0074] The fouling rate of this comparative example is 5.2 g / m 2 • h, heat transfer coefficient 1900 W / m 2 • C.

[0075] Comparative Example 3

[0076] This comparative example is based on Example 1, the process sequence of the transition hydrophobic layer is reversed, specifically including: first spraying 5wt% perfluorooctyltriethoxysilane (spraying pressure 0.3 MPa), and then laser processing micro-pits (50W, diameter 5-10 μm, depth 2 μm, length ratio 25%).

[0077] The contact angle of the transition hydrophobic layer in this comparative example is θ = 85°. The fouling rate is 4.8 g / m 2 • h.

[0078] The surface fouling layer of the main hydrophobic layer in the above Example 1 is loose, with a thickness of 38 μm, while the hydrophilic surface of Comparative Example 1 forms a dense fouling layer with a thickness of 320 μm, and after reversing the process sequence of the transition hydrophobic layer in Comparative Example 3, the thickness of the transition hydrophobic layer fouling layer partially peels off to 210 μm.

[0079] After running for 500 h, the heat transfer coefficient of Example 1 can still be maintained at more than 2500 W / m 2 • C, and the heat transfer coefficient of Comparative Example 1 decreases to 1600 W / m 2 • C after running for 200 h.

[0080] Comparative Example 4

[0081] A commercially available scale inhibitor (Sunnes SN-203, dosage 50 mg / L) is used

[0082] The fouling rate is 6.8 g / m 2 • h, heat transfer coefficient 2300 W / m 2 • C.

[0083] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A scale-resistant MVR evaporator, comprising: a scale-reducing... The evaporator comprises a membrane 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 inlet of the separator (2). The bottom outlet of the separator (2) and the bottom outlet 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). The falling film evaporator (1) is characterized in that it includes a distributor (11), a steam chamber (12), and a falling film tube (13). The falling film tube (13) passes through the steam chamber (12) vertically. The distributor (11) is located above the falling film tube (13) and is used to distribute the fed high-salt wastewater. The inner surface of the falling film tube (13) is decorated with... There is a gradient layer (14), the contact angle of the surface of the gradient layer (14) gradually increases from top to bottom. The gradient layer (14) includes, from top to bottom, a main hydrophilic layer (141), a transition hydrophilic layer (142), a transition hydrophobic layer (143), and a main hydrophobic layer (144). The contact angle θ of the main hydrophilic layer (141) is <10°, the contact angle θ of the transition hydrophilic layer (142) is 10°-30°, and the contact angle of the transition hydrophobic layer (143) is <10°-30°. The contact angle θ of the main hydrophobic layer (144) is 60°-90°, the contact angle θ of the main hydrophobic layer (144) is >110°, the main hydrophilic layer (141) accounts for 20-30% of the length of the gradient layer (14), the transition hydrophilic layer (142) accounts for 25-35% of the length of the gradient layer (14), the transition hydrophobic layer (143) accounts for 20-30% of the length of the gradient layer (14), and the main hydrophobic layer (144) accounts for 15-25% of the length of the gradient layer (14).

2. The anti-scaling MVR evaporator as described in claim 1, characterized in that, The preparation method of the main hydrophilic layer (141) includes: immersing the main hydrophilic layer (141) region of a titanium falling film tube (13) into an electrolyte and connecting it to the anode of a power supply, connecting the cathode of the power supply to a carbon rod immersed in the electrolyte, starting the pulse power supply, electrolyzing, and then cleaning and drying to obtain the main hydrophilic layer. The electrolyte contains 10 g / L Na2SiO3 and 2 g / L KOH.

3. The anti-scaling MVR evaporator as described in claim 2, characterized in that, The electrolysis treatment conditions include: temperature of 25-30℃, 400V pulsed DC, frequency of 1000Hz, and electrolysis treatment for 10-20 minutes.

4. The anti-scaling MVR evaporator as described in claim 1, characterized in that, The preparation method of the transition hydrophilic layer (142) includes: using a galvanometer scanning system to process a parallel microgroove array in the region of the transition hydrophilic layer (142), so that the direction of the microgroove is at a 45° angle to the fluid flow direction, and then cleaning and drying after processing.

5. The anti-scaling MVR evaporator as described in claim 4, characterized in that, The processing laser wavelength is 1064nm, the power is 200W, the scanning speed is 50mm / s, the line spacing is 20μm, the width of the parallel microgrooves is 20μm, and the depth is 5μm.

6. The anti-scaling MVR evaporator as described in claim 1, characterized in that, The preparation method of the transition hydrophobic layer (143) includes: firstly, using a laser to process a micro-pit array on the surface of the transition hydrophobic layer (143) region, then spraying perfluorooctyltriethoxysilane on the surface of the transition hydrophobic layer (143) region, and then heating to 120°C for baking treatment for 20-40 minutes.

7. The anti-scaling MVR evaporator as described in claim 6, characterized in that, The laser power is 50W, and the diameter of the micro-pit is 5-10μm, with a depth of 2μm.

8. The anti-scaling MVR evaporator as described in claim 1, characterized in that, The method for preparing the main hydrophobic layer (144) includes: exposing the main hydrophobic layer (144) region in the CVD reaction chamber and aligning it with the gas nozzle, heating it to 250°C, introducing hexamethyldisilazane and carrier argon, performing a deposition treatment for 2 hours, and then performing a vacuum annealing treatment at 300°C for 1 hour.

9. The anti-scaling MVR evaporator as described in claim 8, characterized in that, The gas flow rate of hexamethyldisilazane is 20 sccm, and the argon flow rate is 50 sccm.

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