Self-cleaning anti-blocking falling film evaporator

Abstract

The invention relates to an automatic cleaning anti-blocking falling film evaporator, which mainly comprises a spiral power wheel, an anti-blocking pipe orifice bearing bracket, a pipe orifice cleaning steel wire, a steel wire spiral, an intelligent numerical control cabinet, a liquid distribution disc, a spraying hole cleaning steel wire and an intelligent numerical control cabinet. Falling film liquid flow impacts the steel wire spirals to drive radial vibration of hundreds of times per minute and slow rotation of less than 5 revolutions per minute, uniform and automatic cleaning of the heat exchange tubes is achieved, and possible abrasion of the heat exchange tubes is prevented. And the spiral power wheel utilizes the rotating power obtained by a rapid two-phase flow formed by mixing secondary steam at the outlet section of the heat exchange tube and a falling film liquid flow, so that the power for automatically cleaning the steel wire spiral is enhanced. The spraying hole cleaning steel wire and the pipe opening cleaning steel wire are driven to continuously rotate by utilizing the power of liquid flow impulse, so that timely cleaning and blockage prevention are realized. The intelligent numerical control cabinet can automatically adjust the automatic cleaning strength of the steel wire spiral according to the temperature data of the operation of the evaporator, and periodically assists the steel wire spiral which may stop rotating to recover to rotate again. And the reliability of automatic cleaning is improved.

Description

Technical Field

[0001] The present invention relates to an automatic cleaning and anti-blocking falling film evaporator. It can be widely applied to the continuous automatic cleaning of dirt in the heating tubes of falling film evaporators, and can prevent the blockage of a small amount of debris in the evaporation mother liquor. It is particularly suitable for large falling film evaporators in industries such as alumina, starch, and wastewater treatment. Background Art

[0002] Evaporators are widely used in alumina production. Although the technical level has been greatly improved after two or three decades of continuous improvement on the basis of introduction, the problems of dirt in the heating tubes and blockage by debris still affect the evaporation capacity and energy consumption. It is necessary to stop the machine for cleaning four times a year, and the pickling also affects the service life of the evaporator.

[0003] The rapid self-rotation wire helix automatic cleaning technology for heat exchange tubes (Experimental study on the automatic rotating helix heat transfer technology, Chemical Engineering Equipment Technology, 1997, N5, P4 - 8) has a strong cleaning function and a simple structure. However, it requires a relatively high flow rate inside the heat exchange tubes, and there is also a problem that the heat exchange tubes are worn by the wire helix for automatic cleaning.

[0004] The new automatic cleaning technology of reciprocating wire helix (CN201210374716.9 A falling film evaporator with in-tube vibration spiral reciprocating cleaning, April 9, 2014) better solves the problem of wire helix wearing the heat exchange tubes, but it requires a large heat transfer temperature difference, which is contradictory to the energy saving of multi-effect evaporation and MVR; and the structure is complex, and the existing evaporator body must be modified, which is not convenient for technological transformation applications.

[0005] For the liquid distribution tray widely used in alumina falling film evaporators, the structure of inserting a three-claw type distributor head into the shower holes is easily blocked by debris in the mother liquor, which affects the uniformity of the flow rate at the inlet of the lower heating tubes, affects the heat transfer efficiency of the heating tubes, and hinders the application of mechanical automatic cleaning technology. Because the wire helix in the heating tube with a lower flow rate rotates weakly and is prone to getting stuck and gradually growing dirt; on the contrary, the wire helix in the heating tube with a larger flow rate rotates too fast and induces wear. Summary of the Invention

[0006] An automatic cleaning and anti-blocking falling film evaporator proposed by the present invention focuses on the problems of dirt in the heat exchange tubes, blockage of the secondary liquid distribution tray, and blockage of the heat exchange tube orifices existing in the falling film evaporator for alumina production. It proposes a steel wire spiral automatic cleaning rotation power strengthening technology that combines the spiral power wheel of the fast two-phase flow at the outlet section of the heat exchange tube and the digital intelligent strengthening wave, and also proposes a liquid distribution tray anti-blocking technology and a heat exchange tube orifice anti-blocking technology. Under the impulse of the falling film flow with the existing circulation pump flow rate, the steel wire spiral in the heat exchange tube can generate radial vibrations hundreds of times per minute to knock and clean the dirt, and it can also rotate slowly in the circumferential direction at a speed limited to less than 5 revolutions per second for uniform cleaning, avoiding the possibility of wearing the heat exchange tube. This new technical solution is simpler in structure and higher in reliability than the reciprocating spiral automatic cleaning structure; it does not require any modification to the original evaporator body, facilitating the automatic cleaning technical transformation of the existing falling film evaporator.

[0007] The present invention is realized through the following technical solutions:

[0008] An automatic cleaning and anti-blocking falling film evaporator mainly consists of heat exchange tubes, anti-blocking orifice bearing frames, orifice cleaning steel wires, steel wire spirals, spiral power wheels, liquid distribution trays, shower hole cleaning steel wires, and intelligent numerical control cabinets. The liquid distribution tray is located above the heat exchange tubes. The steel wire spiral, spiral power wheel, and anti-blocking orifice bearing frame form an automatic cleaning mechanism. The steel wire spiral is suspended at the lower end of the anti-blocking orifice bearing frame. The spiral power wheel is suspended at the lower end of the steel wire spiral. The steel wire spiral is impacted by the falling film liquid flow, generating radial vibrations hundreds of times per minute to knock the dirt on the inner wall of the heat exchange tube to achieve automatic cleaning. Under the impact of the falling film flow, the steel wire spiral can automatically limit its rotation speed to less than 5 revolutions per minute for slow self-rotation, which not only realizes the uniform cleaning of the dirt on the inner wall of the heat exchange tube in the circumferential direction but also eliminates the possibility of wearing the heat exchange tube from the mechanism where the PV value is less than the lowest PV value at which wear occurs.

[0009] The anti-blocking orifice bearing frame is produced by plastic injection molding with corrosion resistance, high temperature resistance, and low friction coefficient, such as PFA, PEEK, PPS modified with PTFE, etc. The load of the steel wire spiral acting on the orifice bearing is very small, less than 10 N, so the size of the long-life bearing washer can be very small, and an outer diameter of φ10 is sufficient. With such a small load, a low friction coefficient, and a small radius of the rotational friction force, the self-rotation friction resistance moment of the orifice bearing is very small, ensuring that the steel wire spiral can rotate reliably for self-cleaning without any external power.

[0010] The bearing hole diameter of the anti-blocking orifice bearing frame is 2.5 - 3.5 mm, the height H5 of the bearing part is about 15 mm, the height H4 of the anti-blocking door frame is in the range of 40 - 50 mm, ensuring that the inlet window area is large enough; the width ξ of the adjustment slit is 1.5 - 2.5 mm, adapting to different wall thicknesses of the heat exchange tubes and facilitating installation; the height H3 of the fixed pipe section is required to be more than 40 mm to ensure the reliability of fixation.

[0011] There are two structural solutions for the wire helix to be suspended on the anti-blocking pipe orifice bearing bracket.

[0012] The first is the wire hook shaft suspension solution. The straight connection section at the upper part of the automatic cleaning wire helix is cleaned. During installation, it is bent into a hook shaft of about 90 degrees and suspended on the end face of the anti-blocking pipe orifice bearing to form a sliding friction pair. Moreover, the outer extension section of the hook shaft is bent twice to form an integrated pipe orifice cleaning wire. This structure is the simplest, most economical, and very reliable. It continuously cleans the possible blockages and fundamentally prevents the possibility of cumulative blockage at the inlet of the heat exchange tube. The disadvantage is that the wire needs to be bent manually three times during installation.

[0013] The second is the hook bolt shaft suspension solution. The hook bolt shaft is sleeved with three high wear-resistant and self-lubricating fluoroplastics washers to form a sliding bearing. The M3 hook bolt shaft has sufficient strength and stiffness. The fluoroplastics washer φ10 / φ3.1 is sufficient, with a thickness of 2 - 5mm. The rotation reliability of three washers is higher than that of a single washer, and the service life is also longer. Compared with the first solution, the structure is slightly more complex. The pipe orifice cleaning wire is convenient for factory production, with a standard and regular shape and better quality; moreover, it can be pre-installed, making on-site installation more convenient. The disadvantage is that the automatic cleaning wire helix and the M3 hook bolt shaft cannot be directly suspended, forming a high friction pair that is prone to wear, and a wear-resistant plastic connecting plate must be added.

[0014] The diameter range of the pipe orifice cleaning wire is 0.8 - 1.8mm, which is selected according to the self-rotation torque of the wire helix. Avoid selecting too thick wire to prevent the automatic cleaning failure of jamming the wire helix.

[0015] The wire helix is an important component that combines the automatic cleaning function and the automatic cleaning power function. The wire diameter range is 1.2 - 2.2mm, and the clearance range between the outer diameter of the helix and the inner wall of the heat exchange tube is 2.5 - 6.0mm. The pitch is 0.8 - 1.5 times the inner diameter of the heat exchange tube, and the design and selection of the coefficient size have a consistent relationship with the falling film flow rate inside the heat exchange tube.

[0016] The main function of the spiral power wheel is to utilize the relatively fast outlet flow rate of the secondary steam at the outlet section of the heat exchange tube to accelerate the outlet movement speed of the falling film liquid, form a vapor-liquid mixed two-phase spiral flow, push the spiral power wheel, and significantly increase the self-rotation torque of the wire helix. On a pilot test bench with a length of 12 meters and heating tube size φ57X3.5, during the actual measurement of the atmospheric evaporation sample, the total self-rotation torque increased by more than 30% compared with that without the spiral power wheel.

[0017] The spiral power wheel structure consists of two parts: a hollow tube hub and spiral blades. It is not only convenient for extrusion production, but more importantly, different optimized solutions of the spiral power wheel with different evaporation pressures can be obtained by designing hollow tube hubs with different outer diameters. In the pressurized evaporation process, a solution with a hollow tube hub having a smaller spiral angle β and a larger cross-sectional ratio D6 / D0 can be adopted to increase the actual flow velocity of the two-phase flow and the torque of the spiral power wheel. In the vacuum evaporation process, a solution with a hollow tube hub having a larger spiral angle β and a smaller cross-sectional ratio D6 / D0 can be adopted to reduce the actual flow velocity of the two-phase flow and the flow resistance of the spiral power wheel. The diameter gap between the outer diameter D7 of the spiral power wheel and the inner diameter of the heat exchange tube is in the range of 2.5 - 5.0 mm, and the thickness δ of the spiral blade is 2 - 3 mm. The spiral angle β is in the range of 25 - 55°, and the greater the evaporation pressure, the smaller the value of the spiral angle β. The outer diameter D6 of the hollow tube hub 32 is 0.2 - 0.5 times the inner diameter D0 of the heat exchange tube, and the higher the evaporation pressure, the larger the design coefficient value.

[0018] The size range of the diameter gap between the spiral power wheel and the inner wall of the heat exchange tube is 2 - 5 mm, mainly considering the size and quantity of the blocked debris in the falling film liquid flow. The spiral direction of the spiral power wheel must be the same as that of the wire spiral. The size of the spiral angle β of the spiral power wheel is between 25 - 55°, and it has an inverse relationship with the evaporation pressure because the volume of the secondary steam with the same evaporation water volume is inversely proportional to the evaporation pressure. The length of the spiral power wheel is 150 - 250 mm, and its value has a consistent relationship with the size of the spiral angle.

[0019] Another advantage of the spiral power wheel technology is that it is convenient for the complete automatic cleaning of the tail section of the heat exchange tube, eliminates the worry of mutual entanglement of the wire spirals extending outwards, and improves reliability.

[0020] The spiral power wheel is made of plastics that are heat-resistant, corrosion-resistant, and wear-resistant, and is produced by the most economical extrusion process.

[0021] The basic functions of the two-stage liquid distributor are to improve the uniformity of the mother liquor flow rate into each heat exchange tube as much as possible. However, the secondary liquid distributor is prone to blockage. Therefore, at the inlet of its shower holes, there is a rotatable cleaning wire for the liquid distributor. The horizontal sections at both ends of the cleaning wire are sleeved with self-lubricating fluoroplastic tubes. A circular hook is designed in the middle of the cleaning wire for the liquid distributor to hang the conical wire helix below. The average flow rate of the liquid flowing down through the shower holes is relatively large, generally about 5 m3 / h. The liquid flowing down through the shower holes impacts the conical wire helix below to rotate itself, driving the cleaning wire to continuously rotate itself to clean the sundries that may remain at the pipe orifice, avoiding accumulation and blockage, and realizing anti-blockage. Another important function of the conical wire helix is to induce the liquid flowing down through the shower holes to be more evenly distributed into each heat exchange tube in the preset area below, avoiding the lack of self-rotation power of the wire helix in the heat exchange tube with a small flow rate until the dirt gradually grows, and preventing the wire helix in the heat exchange tube with a large flow rate from rotating too fast and inducing wear. The wires of the cleaning wire and the conical wire helix have a diameter of 1.8 - 3.0 mm. The diameter D3 of the shower holes is about 60 mm. The cone angle α of the conical wire helix is in the range of 15 - 35°. The large end diameter D2 of the conical wire helix is 0.30 - 0.55 times the diameter D1 of the corresponding heat exchange tube area below.

[0022] The two basic functions of the intelligent numerical control cabinet. First, it displays the temperatures of the heating steam and the secondary steam and their temperature difference in real time. If the temperature difference increases significantly (generally taking 1 °C), it will automatically increase the current frequency of the circulation pump and increase the vibration frequency - vibration intensity - automatic cleaning intensity level of the automatic cleaning wire helix to maintain efficient and stable operation. Second, due to possible problems with the uniformity of the inlet flow rate, or blockage of the falling film liquid flow by some sundries, or other reasons, there may be a situation where individual wire helices stop rotating and it is difficult to resume rotation on their own. Therefore, it is set to automatically increase the falling film flow rate by 20 - 30% every 10 - 30 minutes for 2 - 3 minutes to assist the restart of the stopped wire helices, thereby effectively improving the reliability of automatic cleaning. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of a scheme for an automatic cleaning and anti-blocking falling film evaporator of the present invention.

[0024] Figure 2 It is a schematic diagram of a scheme for the anti-blocking structure of the liquid distributor.

[0025] Figure 3 It is a schematic diagram of the wire hook shaft of the wire helix suspension anti-blocking pipe orifice bearing frame.

[0026] Figure 4 It is a schematic diagram of the hooked bolt shaft of the wire helix suspension anti-blocking pipe orifice bearing frame.

[0027] Figure 5 It is a schematic diagram of the structure of the hollow pipe spiral power wheel. Detailed Embodiments

[0028] The following will further describe the present invention in detail in conjunction with Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 .

[0029] In the figure, 1 is the secondary liquid distribution tray, 2 is the cleaning wire for the falling holes, 3 is the conical wire helix, 4 is the primary liquid distribution tray, 5 is the anti-blocking pipe orifice bearing bracket, 6 is the pipe orifice cleaning wire, 7 is the straight connection section of the wire helix, 8 is the heating steam pipe, 9 is the wire helix, 10 is the heat exchange tube, 11 is the spiral power wheel, 12 is the condensate water pipe, 13 is the secondary steam pipe, 14 is the intelligent numerical control cabinet, 15 is the steam-liquid separation bottom tank, 16 is the circulation pump, 17 is the feeding pipe, 18 is the flowmeter, 19 is the fluoroplastic pipe, 20 is the wire hook shaft, 21 is the bearing part, 22 is the anti-blocking door frame, 23 is the adjustment slit, 24 is the fixed pipe section, 25 is the wear-resistant plastic connecting plate, 26 is the wear-resistant fluoroplastic bearing washer, 27 is the hook bolt shaft, 28 is the double nut, 29 is the suspension hole, 30 is the hollow pipe hub, and 31 is the spiral blade

[0030] An automatic cleaning and anti-blocking falling film evaporator mainly consists of a wire helix 9, a spiral power wheel 11, a heat exchange tube 10, an anti-blocking pipe orifice bearing bracket 5, a pipe orifice cleaning wire 6, a secondary liquid distribution tray 1, and a cleaning wire 2 for the falling holes, and an intelligent numerical control cabinet 14. The secondary liquid distribution tray 1 is located above the heat exchange tube 10. The wire helix 9, the spiral power wheel 11, and the anti-blocking pipe orifice bearing bracket 5 form an automatic cleaning mechanism. The wire helix 9 is suspended at the lower end of the anti-blocking pipe orifice bearing bracket 5. The spiral power wheel 5 is suspended at the lower end of the wire helix 9. The wire helix 9 is impacted by the falling film liquid flow, generating radial vibrations hundreds of times per minute, knocking the dirt on the inner wall of the heat exchange tube 10 to achieve automatic cleaning. Under the impact of the falling film flow, the wire helix 9 can automatically limit its speed to rotate slowly at less than 5 revolutions per minute, which not only realizes the uniform cleaning of the dirt on the inner wall of the heat exchange tube 10 in the 360-degree circumferential direction but also makes the PV value lower than the lowest PV value for wear, preventing the possibility of wear of the heat exchange tube (10);

[0031] The anti-blocking pipe orifice bearing bracket 5 is produced by plastic injection molding with corrosion resistance, high temperature resistance, and low friction coefficient, such as PFA, PEEK, PPS modified with PTFE, etc. The load exerted by the wire helix on the pipe orifice bearing is very small, less than 10 N. Therefore, the size of the long-life wear-resistant fluoroplastic bearing washer 26 can be designed to be very small, with an outer diameter of φ10 being sufficient. With such a small load, a low self-lubricating friction coefficient, and a small radius of the rotational frictional force, the self-rotational frictional resistance moment of the pipe orifice bearing is very small, which can reliably ensure the continuous and uniform rotation of the wire helix 9 for cleaning without any external power.

[0032] The bearing hole diameter of the anti-blocking pipe orifice bearing bracket 5 is 2.5 - 3.5 mm, the height H5 of the bearing part 21 is about 15 mm, the height H4 of the anti-blocking door frame 22 ranges from 40 to 50 mm, ensuring that the inlet window area is large enough; the width ξ of the adjustment seam 23 is 1.5 - 2.5 mm, adapting to the slight difference in the wall thickness of the heat exchange tube 10 for convenient installation; the height H3 of the fixed pipe section 24 is required to be more than 40 mm to ensure the reliability of fixation.

[0033] There are two structural schemes for hanging the wire helix 9 on the anti-blocking pipe orifice bearing bracket 5.

[0034] The first is the wire hook shaft 20 hanging scheme. The straight connection section 7 of the wire helix for automatic cleaning is bent into a wire hook shaft 20 of about 90 degrees during installation and hung on the end face of the anti-blocking pipe orifice bearing 5 to form a sliding friction pair. The outer extension section of the wire hook shaft 20 is bent twice to form an integrated pipe orifice cleaning wire 6. This structure is the simplest, most economical and reliable, continuously cleaning the possible blockages, and fundamentally preventing the possibility of cumulative blockage at the inlet part of the heat exchange tube 10. The disadvantage is that it needs to be manually bent three times during installation.

[0035] The second is the hanging scheme of the hook bolt shaft 27. The hook bolt shaft 27 is sleeved with three self-lubricating and highly wear-resistant fluoroplastic bearing washers 26 to form a sliding bearing. The strength and stiffness of the M3 hook bolt shaft 27 are sufficient. The wear-resistant fluoroplastic bearing washer φ10 / φ3.1 is sufficient, with a thickness of 2 - 5 mm. The rotation reliability of the three washers is higher than that of a single washer, and the service life is also longer. Compared with the first scheme, the structure is slightly more complex. The pipe orifice cleaning wire 6 can be produced in a factory, with a standard and regular shape and better quality; moreover, it can be pre-installed, making on-site installation more convenient. The disadvantage is that the automatic cleaning wire helix 9 and the M3 hook bolt shaft cannot be directly hung, forming a high friction pair that is prone to wear, and a wear-resistant plastic connecting plate 25 must be installed.

[0036] The diameter range of the pipe orifice cleaning wire 6 is 0.8 - 1.8 mm, which is selected according to the self-rotation torque of the wire helix 9. Avoid selecting too thick wire to prevent the automatic cleaning failure of jamming the wire helix 9.

[0037] The wire helix 9 is an important component that combines the automatic cleaning function and the automatic cleaning power function. The wire diameter range is 1.2 - 2.2 mm, and the clearance range between the outer diameter of the helix and the inner wall of the heat exchange tube 10 is 2.5 - 6.0 mm. The pitch is 0.8 - 1.5 times the inner diameter of the heat exchange tube 10, and the coefficient size design selection has a consistency relationship with the falling film flow rate inside the heat exchange tube 10.

[0038] The main function of the spiral power wheel 11 is to utilize the secondary steam with a relatively high flow rate at the outlet section of the heat exchange tube 10 to accelerate the outlet movement speed of the falling film liquid, form a spiral flow of the vapor-liquid mixed two-phase, push the spiral power wheel 11, and effectively increase the total driving torque of the self-rotation of the wire spiral 9. On a pilot test bench with a length of 12 m and heating tube dimensions of φ57X3.5, the actual measurement of the sample for atmospheric evaporation shows that the total self-rotation driving torque increases by more than 30% compared with the case without the spiral power wheel 11, and the effect is remarkable.

[0039] The spiral power wheel 11 is composed of two parts: a hollow tube hub 30 and spiral blades 31. This not only facilitates extrusion production, but more importantly, by changing the hollow tube hub 30 with different cross-sectional area ratios, an optimized solution for the spiral power wheel 11 with different evaporation pressures can be obtained. In the pressurized evaporation process, a solution with a smaller spiral angle β and a larger cross-sectional ratio D6 / D0 of the hollow tube hub 30 can be adopted to accelerate the actual flow rate of the two-phase flow and increase the driving torque of the spiral power wheel 11. In the vacuum evaporation process, a solution with a larger spiral angle β and a smaller cross-sectional ratio D6 / D0 of the hollow tube hub 30 can be adopted to reduce the actual flow rate of the two-phase flow and reduce the flow resistance of the spiral power wheel 11. The diameter clearance between the outer diameter D7 of the spiral power wheel 11 and the inner diameter of the heat exchange tube 10 ranges from 2.5 to 5.0 mm, and the thickness δ of the spiral blade 31 is 2 to 3 mm. The spiral angle β ranges from 25 to 55°. The greater the evaporation pressure, the smaller the value of the spiral angle β. The outer diameter D6 of the hollow tube hub 32 is 0.2 to 0.5 times the inner diameter D0 of the heat exchange tube 10. The higher the evaporation pressure, the larger the design coefficient value. The diameter clearance between the spiral power wheel 11 and the inner wall of the heat exchange tube 10 ranges from 2 to 5 mm, mainly considering the size and quantity of the blocking debris in the falling film liquid flow. The spiral direction of the spiral power wheel 11 must be the same as that of the wire spiral 9.

[0040] The length of the spiral power wheel 11 is 150 to 250 mm, and its value has a consistent relationship with the size of the spiral angle. Another advantage of the spiral power wheel technology 11 is that it facilitates the complete automatic cleaning of the tail section of the heat exchange tube 10, eliminates the worry of mutual entanglement of the extended wire spiral 9, and effectively improves the reliability.

[0041] The spiral power wheel 11 is made of a plastic that is resistant to high temperature, corrosion, and wear, and extrusion production is the most economical.

[0042] The basic functions of both the two-stage liquid distributor trays are to improve the uniformity of the mother liquor flow rate entering each wire helix 10 as much as possible. However, the secondary liquid distributor tray 1 is relatively prone to blockage. Therefore, a rotatable cleaning wire 2 for the downcomer holes is provided at the downcomer hole part, and self-lubricating fluoroplastic tubes are sleeved on the horizontal sections at both ends of the cleaning wire 2 for the downcomer holes. A circular hook is designed in the middle of the cleaning wire 2 for the downcomer holes to hang the conical wire helix 3 below. The average flow rate of the liquid flowing down through the downcomer holes is relatively large, generally reaching about 5 m3 / h. The liquid flowing down through the downcomer holes impacts the conical wire helix 3 below to rotate self-rotationally, driving the cleaning wire 2 for the downcomer holes to rotate continuously, cleaning the sundries that may remain at the downcomer hole openings, avoiding accumulation and blockage, and realizing anti-blockage. Another important function of the conical wire helix 3 is to induce the liquid flowing down through the downcomer holes to enter each heat exchange tube 10 in the preset target area below in a relatively uniform distribution, avoiding the weak self-rotation of the wire helix 9 in the wire helix 10 with a small flow rate, gradually growing dirt, and also preventing the wire helix 9 in the wire helix 10 with a large flow rate from rotating too fast and inducing wear. The wires of the cleaning wire 2 for the downcomer holes and the conical wire helix have a diameter of 1.8 - 3.0 mm. The diameter D3 of the downcomer holes is about 60 mm. The cone angle α of the conical wire helix 3 ranges from 35° to 60°. The large-end diameter D2 of the conical wire helix 3 is 0.25 - 0.5 times the diameter D1 of the corresponding wire helix 10 area below.

[0043] The two basic functions of the intelligent numerical control cabinet 14. First, it displays the temperatures of the heating steam and the secondary steam and the temperature difference between them in real time. If the temperature difference increases significantly (generally taking 1°C), it will automatically increase the current frequency of the circulation pump 16 and increase the vibration frequency - vibration intensity - automatic cleaning intensity level of the automatic cleaning wire helix 9 to maintain efficient and stable operation. Second, due to possible problems with the uniformity of the inlet flow rate, or blockage of the falling film liquid flow by some sundries, or other reasons, after the wire helix 9 of an individual heat exchange tube 10 stops rotating, it is unable to resume self-rotation on its own. For this reason, it is set to increase the falling film flow rate by 20 - 30% every 10 - 30 minutes and last for 2 - 3 minutes to assist the restart of the stopped wire helix 9, thereby further improving the reliability of automatic cleaning.

Claims

1. An automatic cleaning anti-blocking falling film evaporator, mainly comprising a heat exchange tube (10), an anti-blocking pipe mouth bearing frame (5), a pipe mouth cleaning wire (6), a steel wire spiral (9), a spiral power wheel (11), a secondary liquid distribution plate (1), a falling hole cleaning wire (2), and an intelligent numerical control cabinet (14), and the technical features are: Steel Wire The spiral (9) is a component integrating the automatic cleaning function and the automatic cleaning power function. The anti-blocking pipe mouth bearing frame (5), the steel wire spiral (9), and the spiral power wheel (11) form an automatic cleaning mechanism. Under the power drive of the falling film liquid flow impacting the steel wire spiral (9), hundreds of radial vibrations per minute and slow rotations of less than 5 revolutions per minute are generated, so that the dirt on the inner wall of the heat exchange tube (10) is evenly cleaned in the circumferential direction. The PV value is lower than the minimum value that causes wear, thereby preventing the possibility of wear of the heat exchange tube (10). The anti-blocking pipe mouth bearing frame (5) has a bearing hole diameter of 2.5 to 3.5 mm, a bearing portion (21) height H5 of about 15 mm, an anti-blocking door frame (22) height H4 of 40 to 50 mm, an adjustment gap (23) width ξ of 1.5 to 2.5 mm, and a fixed pipe section (24) height H3 of more than 40 mm; the load of the steel wire spiral (9) on the pipe mouth bearing is less than 10 N, and the outer diameter of the long-life wear-resistant fluoroplastic bearing washer (26) is The small rotational friction radius, coupled with the self-lubricating low friction coefficient of the fluoroplastic bearing washer (26), jointly ensure that the wire spiral (9) can reliably perform automatic cleaning movement without the need for external power; The straight section (7) of the automatic cleaning wire spiral (9) is bent into a wire hook shaft (20), which is hung on the end surface of the anti-blocking pipe mouth bearing (5) and then bent twice to form a pipe mouth cleaning wire (6), which is integrated with the wire spiral (9) to self-rotate and clean, thereby preventing the inlet of the heat exchange pipe (9) from being blocked; The spiral power wheel (11) utilizes the rapid two-phase flow of the secondary steam and the falling film liquid flow mixed at the outlet section of the heat exchange tube (10) to generate rotational power, so that the self-rotation torque of the steel wire spiral (9) is increased by about 30%; the hollow tube hub (30) of the power spiral power wheel (11) structure is convenient for the outer diameter D6 to be within the range of 0.2 to 0.5 times the inner diameter D0 of the heat exchange tube (10), and is designed according to the principle that the higher the evaporation pressure, the larger the coefficient value, so as to obtain the optimal solution under different evaporation pressure conditions; the hollow tube hub (30) structure is also The extrusion production of the spiral power wheel (11) is facilitated; the spiral direction of the spiral power wheel (11) must be the same as that of the steel wire spiral (9), and the spiral angle β is selected in the range of 25 to 55 degrees, in principle, it is inversely related to the evaporation pressure; the length of the spiral power wheel (11) is in the range of 150 to 250 mm, and the value is selected according to the consistency relationship with the spiral angle β; the diameter gap between the spiral power wheel (11) and the inner wall of the heat exchange tube (10) is in the range of 2 to 5 mm, mainly considering the size and amount of blocking debris in the falling film liquid flow; The secondary liquid distribution plate (1) is relatively easy to be blocked, so a rotatable drainage hole cleaning wire (2) is arranged at the drainage hole, and the horizontal sections at both ends of the wire are covered with self-lubricating fluoroplastic tubes (), and the circular hook in the middle hangs a conical wire spiral (3); under the impulse of the liquid flowing down the drainage hole, the drainage hole cleaning wire (2) is driven to rotate together, and the debris trapped in the drainage hole mouth is cleaned in time to prevent blockage; another important function of the conical wire spiral (3) is to guide the liquid flowing down the drainage hole to be more evenly drenched to the heat exchange tube (9) in the preset drainage area below; the diameter of the drainage hole cleaning wire (2) is 1.8 to 3.0 mm; the cone angle α of the conical wire spiral (3) is in the range of 15 to 35 degrees, and the large end diameter D2 of the conical wire spiral (3) is 0.30 to 0.55 times the diameter D1 of the preset drainage area of ​​the heat exchange tube (9) below (to be tested again). The basic functions of the intelligent numerical control cabinet (14) are: first, to display the temperature of the heating steam and the secondary steam and the temperature difference between the two in real time, and to automatically increase the current frequency of the circulation pump (16) and increase the level of automatic cleaning intensity when the temperature difference increases by more than 1°C, so as to maintain stable and efficient operation; second, to periodically increase the falling film flow rate of the circulation pump (16) by 20-30% every 10-30 minutes for 2-3 minutes to assist in the restart of the stopped wire spiral (9) and improve the reliability of automatic cleaning.

2. An automatic cleaning and anti-blocking falling film evaporator according to claim 1, characterized in that: The steel wire spiral (9) is suspended on the anti-blocking pipe mouth bearing frame (5) through a hook bolt shaft (27), and the hook bolt shaft (27) is covered with three self-lubricating, high wear-resistant fluoroplastic bearing washers (26) to form a sliding bearing; the wear-resistant fluoroplastic bearing washers Double nut (28) clamps the ring of the pipe cleaning wire (6) on the hook bolt shaft (27).

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