A pre-filter device and cleaning method for aluminum heat exchange tube type seawater desalination system

Abstract

The present invention discloses a pre-filter device for an aluminum heat exchange tubular desalination system. The pre-filter device is arranged at the inlet end of the cold source side of the low-temperature multi-effect desalination system. The pre-filter device includes a plurality of pre-filter units. The plurality of pre-filter units are arranged in a mother pipe split form. The pre-filter units include a seawater booster pump, a front-end pressure transmitter, an ion trap, a rear-end pressure transmitter, a filter, a VSD logic control system and a backwash device. The backwash device includes a backwash buffer tank, a backwash pump and a backwash filter. The purpose of the present invention is to provide a pre-filter device for an aluminum heat exchange tubular desalination system, which can reduce the concentration of corrosive metal ions in seawater to a negligible level, effectively protect aluminum alloy heat exchange tubes from being attacked by such ions to generate dynamic current corrosion, ensure the safe and stable operation of the desalination device, and reduce the frequency of disassembly and plugging of the heat exchange tube bundle of the effect evaporator.

Description

Technical Field

[0001] The invention relates to the technical field of seawater desalination, and in particular to a pre-filter device of an aluminum heat exchange tube type seawater desalination system and a cleaning method. Background Art

[0002] The heat exchange process of the low-temperature multi-effect seawater desalination device is mainly evaporation and condensation. The original seawater or concentrated seawater is evenly distributed on the outer surface of the heat exchange tube inside the effect evaporator through the spray system to achieve heat exchange in a thin film. The seawater on the outer wall of the tube absorbs the latent heat of steam and vaporizes. The steam on the inner wall of the tube condenses into fresh water when it is cooled. The above process is repeated to achieve the desalinated water production process. At present, in the low-temperature multi-effect seawater desalination device that mainly uses aluminum alloy heat exchange tubes as the main heat exchange medium, except for the three layers of heat exchange tubes on the upper part of the effect evaporator, which are made of titanium alloy, the remaining heat exchange tubes are mainly aluminum alloy tubes. Therefore, delaying the corrosion of the heat exchange tubes has far-reaching significance for the fresh water production and service life of the seawater desalination device.

[0003] The existing low-temperature multi-effect seawater desalination system (thermal method) desalination process generally has low requirements for the quality of seawater entering the evaporator of the effect body. Its seawater pretreatment process is mainly achieved through coagulation and sedimentation tanks, which are composed of coagulation tanks, sand injection tanks, maturation tanks, and sedimentation tanks. It can remove most of the suspended matter and mud in the seawater to meet the turbidity requirements of the desalinated water. However, for organic matter, microorganisms, bacteria and algae, especially Fe, which has a corrosive effect on aluminum alloy heat exchange tubes, 3+ , Mn 2+ Cations and other corrosive metal ions cannot be effectively removed. After contacting the aluminum alloy heat exchange tubes of the desalination device, a replacement reaction occurs, causing local corrosion and perforation of the heat exchange tubes, resulting in reduced desalination water production efficiency of the evaporator of the desalination device or even the inability to operate normally. Even if a certain amount of scale inhibitors and corrosion inhibitors are added to the seawater, the corrosion intensity of the aluminum alloy heat exchange tubes can only be alleviated to a certain extent. When the corrosive ions contact the aluminum alloy heat exchange tubes, a replacement reaction will still occur, causing local corrosion and perforation of the heat exchange tubes, and it is impossible to fundamentally solve the problem of local corrosion of the heat exchange tubes of the aluminum alloy heat exchange tube desalination device.

[0004] The low-temperature multi-effect seawater desalination device is an evaporator group composed of multiple effect evaporators connected in series. Each evaporator contains 12,000 heat exchange tubes, and the two ends of the heat exchange tubes are closed by partitions and cannot be directly observed, making it very difficult to determine the specific location of the heat exchange tubes where corrosion occurs.

[0005] At present, the method used to determine the location of the heat exchange tube at the corrosion site is as follows: 1) During the operation of the desalination plant, the desalinated water of each effect evaporator is sampled and tested for conductivity, and the effect group where the heat exchange tube at the corrosion site is located is preliminarily determined. 2) During the shutdown period of the desalination plant, the baffles at both ends of the heat exchange tube of the corresponding effect group are removed. 3) A comprehensive water distribution test is carried out on the spray system, the location of the leaking heat exchange tube is marked, and the baffles at both ends are restored after isolating the heat exchange tube by plugging.

[0006] Due to the dense arrangement of heat exchange tubes in the evaporator and the relatively small space of the partition, the implementation process is difficult, time-consuming, labor-intensive, and labor-intensive. There are also large construction safety risks and many uncontrollable factors, which cause the desalination unit to be unable to be put into operation for a long time, affecting the long-term stable operation of the system. Therefore, the method of manually plugging the heat exchange tubes is not ideal.

[0007] According to the process requirements of the existing low-temperature multi-effect seawater desalination device, its heat exchange tube needs to be an independent sealed heat exchange tube section to prevent seawater from leaking to the fresh water side along the overlapping joints and affecting the quality of desalinated water. At the same time, due to the huge number of heat exchange tubes and the structural space limitations of the effect evaporator, it is impossible to achieve the conditions for the overall replacement of the heat exchange tubes. The current method of dealing with this type of problem is only to temporarily block the two ends of the heat exchange tubes at the corroded and leaking parts to maintain continued use, but the blocking of the heat exchange tubes will inevitably cause the heat exchange area of ​​the cold source (seawater) and heat source (steam) inside the effect evaporator to decrease, thereby causing a decrease in the heat exchange efficiency of the seawater desalination device. In the long run, it will lead to a significant reduction in the desalination water production efficiency of the effect evaporator of the low-temperature multi-effect seawater desalination device, and even make it impossible to put it into normal production operation. Summary of the invention

[0008] In view of the above problems, the purpose of the present invention is to provide a pre-filter device and cleaning method for an aluminum heat exchange tube desalination system, which solves the problem that the aluminum heat exchange tube desalination device contains trace amounts of Fe 3+ , Mn 2+ Cations and other corrosive metal ions, after contacting the aluminum alloy heat exchange tubes of the desalination device, undergo a replacement reaction, causing local corrosion and perforation of the heat exchange tube bundle, resulting in a reduction in the desalination water production efficiency of the effect evaporator of the desalination device, or even the inability to operate normally. The technical solution proposed by the present invention can reduce the concentration of corrosive metal ions in seawater to a negligible level, effectively protect the aluminum alloy heat exchange tubes from being attacked by such ions and causing galvanic corrosion, ensure the safe and stable operation of the desalination device, and reduce the frequency of disassembly and plugging of the heat exchange tube bundle of the effect evaporator.

[0009] The technical solution adopted by the present invention to solve the above technical problems is: a pre-filter device of an aluminum heat exchange tube type seawater desalination system, a pre-filter device is arranged at the inlet end of the cold source side of the low-temperature multi-effect seawater desalination system, the pre-filter device includes a plurality of pre-filter units, and the plurality of pre-filter units are arranged in a mother pipe split form;

[0010] The pre-filtration unit includes a seawater booster pump, a front-end pressure transmitter, an ion trap, a rear-end pressure transmitter, a filter, a VSD logic control system and a backwash device. The ion trap is connected to the filter. An isolation electric control valve is provided on the pipeline connecting the seawater booster pump to the ion trap. The backwash device is connected to the inlet and outlet pipe sections of the ion trap through a pipeline.

[0011] The backwash device comprises a backwash buffer tank, a backwash pump, and a backwash filter. The backwash agent enters the backwash buffer tank through a backwash reflux main pipe and is discharged from the backwash buffer tank through a backwash outlet main pipe. The backwash filter is located on the backwash outlet main pipe, and a backwash reflux valve and a backwash regulating valve are provided on the backwash outlet main pipe.

[0012] The isolation electric control valve, the front-end pressure transmitter, the rear-end pressure transmitter, the backwash device, the backwash reflux valve and the backwash regulating valve are respectively connected to the VSD logic control system.

[0013] Furthermore, the ion trap is a vertical pressure vessel with an internal lining and an anti-corrosion coating of glass fiber material. The ion trap is filled with filter material, and the filter material is an aluminum ring made of the same material as the heat exchange tube of the seawater desalination device. The outer diameter of the aluminum ring is 45-65mm, the length is 50-70mm, and the wall thickness is 1.5-2.2mm; a partition is provided inside the ion trap, and the partition is respectively located between the inlet end and the outlet end of the ion trap; and an ion trap exhaust valve for discharging the gas inside the ion trap is provided at the highest point of the top end cover of the ion trap.

[0014] Furthermore, an ion trap drain valve is provided on the pipeline from the ion trap to the drain ditch, the filter is arranged at the rear end of the ion trap and a filter drain valve is provided on the pipeline from the filter to the drain ditch, and the ion trap drain valve and the filter drain valve are respectively connected to the VSD logic control system.

[0015] Furthermore, a backwash inlet valve is provided on the pipeline at the outlet end of the ion trap, and a backwash outlet valve is provided on the pipeline at the inlet end of the ion trap. The backwash inlet valve and the backwash outlet valve are respectively connected to the VSD logic control system.

[0016] Furthermore, the filter is a vertical pressure vessel with an internal lining and an anti-corrosion coating of glass fiber material. A filter cartridge is provided inside the filter. The filter cartridge consists of a filter screen with an upper cylindrical structure and a lower conical structure. The filter screen has a thickness of 1.5-2.5 mm, an opening diameter of 2-2.5 mm, and an opening rate of 42%. A filter hole adjustment ring is provided on the outside of the filter cartridge. A backwash isolation valve is provided in the upper and middle part of the filter cartridge, and the backwash isolation valve is connected to the isolation valve actuator through a valve stem; a zinc sacrificial anode is provided on the lower outer wall of the filter cartridge; a drain pipe is provided at the lowest point of the cone section at the bottom of the filter cartridge, and is connected to the filter drain valve.

[0017] Furthermore, an outlet electric control valve is provided at the outlet end of the filter, the front end pressure transmitter is located in the pipe section in front of the isolation electric control valve, and the rear end pressure transmitter is located in the pipe section in front of the outlet electric control valve of the filter.

[0018] Furthermore, the backwash device also includes a backwash pump inlet pipe and a backwash pump outlet pipe, the backwash pump inlet pipe is located at the bottom of the backwash buffer tank, and the backwash pump outlet pipe is located in the lower middle part of the backwash buffer tank.

[0019] Furthermore, the center line of the backwash pump inlet pipe overlaps with the tank body diameter dividing line of the backwash buffer tank, and the center line of the backwash pump outlet pipe overlaps with the tank body tangent line of the backwash buffer tank.

[0020] A method for cleaning a pre-filter device of an aluminum heat exchange tube type seawater desalination system comprises the following steps:

[0021] S1: According to the monitoring VSD logic control system, the pressure difference change feedback signal of the pressure transmitter on the inlet and outlet sides of the pre-filter unit is monitored, and it is determined that the filter unit group in the pre-filter unit needs to be isolated and backwashed;

[0022] S2: The VSD logic control system implements automatic adjustment of the operating state and controls the start-up of the standby pre-filter unit. The specific control method is as follows: after opening the inlet electric control valve, the isolation electric control valve, and the outlet electric control valve, the seawater booster pump is immediately started (at this time, the ion trap drain valve, the filter drain valve, the backwash inlet valve, and the backwash outlet valve are all in a closed state). After the outlet flow is maintained stable, a switching completion feedback instruction is issued. At the same time, the backwash operation of the filter in the standby filter unit group is performed. First, the filter backwash isolation valve is closed and the filter drain valve is opened. At this time, the filter medium flows out along the filter cartridge at the front end of the backwash isolation valve plate, and then enters the filter cartridge at the rear end of the backwash isolation valve plate from the outside to the inside, and the impurities trapped in the filter cartridge are stripped and discharged along the filter drain valve. When the turbidity of the backwash drainage is detected to be lower than the set value, the filter backwash operation is stopped, and the standby pre-filter unit that needs to be isolated is shut down (at this time, the inlet electric control valve, the isolation electric control valve, and the seawater booster pump of the outlet electric control valve are all in a closed or stopped state);

[0023] S3: Implement backwash purification operation on the ion trap in the idle filter unit group through the VSD logic control system. The specific control method is as follows: start the backwash control process of the backwash device, start the backwash pump, open the backwash regulating valve, backwash inlet valve, and backwash outlet valve (at this time, the ion trap drain valve, filter drain valve, and backwash reflux valve are in a closed state) to perform the backwash reagent circulation cleaning process, and regularly detect the reagent concentration and turbidity, appropriately discharge and replenish the backwash reagent, wait for the backwash reagent concentration to remain constant for a period of time, stop the ion trap backwash operation, open the ion trap drain valve and filter drain valve, and close the backwash inlet valve and backwash outlet valve, and stop the backwash device.

[0024] The advantages of the present invention are:

[0025] 1. The pre-filter device of the present invention can reduce the concentration of corrosive metal ions in seawater to a negligible level, effectively protecting the aluminum alloy heat exchange tubes from galvanic corrosion caused by such ion attacks, and ensuring the safe and stable operation of the desalination device.

[0026] 2. The pre-filter device of the present invention has the advantages of flexible operation, stable performance, high efficiency, short downtime, low maintenance cost and significant effect.

[0027] 3. The pre-filter device of the present invention can save the consumption of scale inhibitors and corrosion inhibitors, and fundamentally solve the problem of local corrosion of heat exchange tubes in aluminum alloy heat exchange tube desalination devices. It can also reduce the frequency of disassembly and plugging of the heat exchange tube bundle of the effect evaporator, save related manpower and material costs, and avoid the desalination device being unable to be put into operation for a long time, affecting the long-term stable operation of the system.

[0028] 4. The pre-filter device of the present invention can effectively solve the problem of reduced heat exchange efficiency due to blockage of heat exchange tubes, resulting in reduced water production ratio of the desalination device, and avoid the technical problem of being unable to achieve the conditions for overall replacement of the heat exchange tube bundle due to structural space limitations of the effective body evaporator.

[0029] 5. The pre-filter device of the present invention can further reduce the content of suspended matter and slime in seawater by setting a clear water tank, an ion trap, and a filter, improve the water quality of the water inlet of the desalination device spray system, and reduce the scouring effect of the spray process on the heat exchange tube bundle. The ion trap is a vertical pressure vessel with an aluminum ring filled with the same filter material as the heat exchange tube of the desalination device (the filter material material can also be replaced according to the material requirements of the subsequent protection device). The specifications, dimensions, and filling amount of the aluminum ring filled inside are all matched with the designed water flux of the pre-filter unit. The filter is a vertical pressure vessel with an internal filter cartridge in the form of an upper columnar structure and a lower cone structure filter screen. The flow flux of the water can be adjusted by the filter hole adjustment ring, and the backwash isolation valve and the filter drain valve are used to realize its own backwash operation process.

[0030] 6. The pre-filter device of the present invention is provided with a backwash device, which can return the scale, mud, mud and other debris peeled off from the ion trap aluminum ring to the backwash buffer tank, thereby ensuring the backwash circulation effect; and the backwash device cancels the stirring device of the traditional buffer tank, and instead adopts a backwash internal circulation method to accelerate the dissolution rate of the cleaning agent, and the center line of the backwash pump inlet pipe overlaps with the dividing line of the cylindrical tank body diameter, and the center line of the backwash pump outlet pipe overlaps with the tangent line of the cylindrical tank body, thereby increasing the mixing disturbance effect of the solution inside the tank body and effectively reducing the device cost investment and maintenance cost expenditure.

[0031] 7. The pre-filter device of the present invention delivers water to the spray system inside the effect evaporator through the corresponding water pump unit group and the corresponding filter unit group of the pre-filter unit. At the same time, according to the monitoring logic control system (VSD), the pressure difference change feedback signal is monitored by the pressure transmitter on the inlet and outlet sides of the filter unit (the accuracy of monitoring the change of trace corrosive ion concentration in an online manner is low, and it does not have the conditions for large-scale application at present), and the operating state is automatically adjusted. The specific control method is as follows: the logic control system (VSD) automatically controls the start-up of the standby pre-filter unit to maintain the outlet flow stable (the outlet pressure transmitter is monitored by the VSD control system to meet the flow demand, and the spray system of the seawater desalination device is prevented from interrupting the flow). At the same time, the pre-filter unit that needs to be stopped and isolated is backwashed and purified, thereby realizing a continuous, automatic and precise control process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a schematic diagram of the structure of the present invention.

[0034] Figure 2 It is a schematic diagram of the connection structure of the ion trap and the filter of the present invention.

[0035] Figure 3 The figure is a working principle diagram of the filter of the present invention.

[0036] Figure 4 It is a cleaning process system diagram of the present invention.

[0037] in:

[0038] 1. Imported electric control valve; 2. Seawater booster pump; 3. Front-end pressure transmitter; 4. Isolation electric control valve; 5. Ion trap; 6. Back-end pressure transmitter; 7. Filter; 8. Export electric control valve; 9. VSD logic control system; 10. Ion trap drain valve; 11. Drain; 12. Filter drain valve; 13. Backwash device; 14. Aluminum ring; 15. Baffle; 16. Backwash inlet valve; 17 Backwash outlet valve; 18. Filter cartridge; 19. Filter hole adjustment ring; 20. Zinc sacrificial anode; 21. Backwash isolation valve; 22. Filter exhaust valve; 23. Backwash buffer tank; 24. Backwash pump; 25. Backwash reflux valve; 26. Backwash regulating valve; 27. Backwash filter; 28. Backwash buffer tank drain valve; 29. ​​Backwash outlet main pipe; 30. Backwash reflux main pipe; 31. Ion trap exhaust valve; DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention 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 therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] Embodiment 1:

[0043] like Figure 1-4As shown, a pre-filter device of an aluminum heat exchange tube seawater desalination system is provided at the inlet end of the cold source side of the low-temperature multi-effect seawater desalination system, the pre-filter device comprises a plurality of pre-filter units, the plurality of pre-filter units are arranged in a mother pipe split form, and can automatically adjust the operation or standby state according to the water demand of the actual operation state of the seawater desalination device; the original seawater passes through the seawater pretreatment coagulation sedimentation tank and enters the clear water tank (also called the buffer water tank, whose internal structure is "S"-shaped, and uses the limited space to maximize the length of the seawater flow channel, effectively settle the suspended matter and slime in the seawater, and reduce the water sand content of the output water), and is transported to the spray system inside the effect evaporator through the corresponding water pump unit group and the corresponding filter unit group of the pre-filter unit At the same time, according to the monitoring VSD logic control system 9, the pressure transmitter on the inlet and outlet sides of the filter unit monitors the pressure difference change feedback signal (the online monitoring of the concentration change of trace corrosive ions has low accuracy and is not currently suitable for large-scale application), and the automatic adjustment of the operating state is implemented. The specific control method is as follows: The VSD logic control system 9 automatically controls the start-up of the standby pre-filter unit to maintain the outlet flow stability (the flow demand is met through the outlet side pressure transmitter of the VSD logic control system 9 to avoid flow interruption accidents in the spray system of the seawater desalination device), and at the same time, the pre-filter unit that needs to be stopped and isolated is subjected to backwashing and purification operations, thereby realizing a continuous, automatic and precise control process, thereby realizing a continuous, automatic and precise control process.

[0044] The arrangement of the pre-filter device of the present invention can be a unit system or a mother pipe system, and the above is only selected for practical use in this embodiment.

[0045] like Figure 2As shown, the pre-filter unit includes a seawater booster pump 2, a front-end pressure transmitter 3, an ion trap 5, a rear-end pressure transmitter 6, a filter 7, a VSD logic control system 9 and a backwashing device 13. The ion trap 5 is connected to the filter 7. An isolation electric control valve 4 is provided on the pipeline connecting the seawater booster pump 2 to the ion trap 5. The isolation electric control valve 4 is specifically located at the inlet end of the ion trap 5. The backwashing process is used to isolate the filter unit group to avoid diffusion and contamination of the backwashing agent. The front-end pressure transmitter 3 is located in the front pipe section of the isolation electric control valve 4, and the rear-end pressure transmitter 6 is located at the outlet electric control valve 4 of the filter 7. The backwash device 13 is connected to the inlet and outlet pipe sections of the ion trap 5 through a pipeline; an inlet electric control valve 1 is arranged on the inlet pipe of the seawater booster pump 2, and an outlet electric control valve 8 is arranged on the outlet pipe of the filter 7. The outlet electric control valve 8 is located at the outlet of the filter 7. The backwash process is used to isolate the filter unit group to avoid diffusion and contamination of the backwash agent; the equipment body and the inlet and outlet pipes of the pre-filter unit are made of fiberglass or corrosion-resistant metal that meet the corresponding parameter requirements, and the inlet and outlet pipe sections of the pre-filter unit are respectively provided with expansion joints, which can reduce the stress damage to the pipeline caused by pipeline vibration and foundation settlement.

[0046] The pre-filtration unit of the present invention at least includes an inlet electric control valve 1, a seawater booster pump 2, a front-end pressure transmitter 3, an isolation electric control valve 4, an ion trap 5, a rear-end pressure transmitter 6, a filter 7, an outlet electric control valve 8, a VSD logic control system 9, an ion trap drain valve 10, a drain ditch 11, a filter drain valve 12, and a backwash device 13, and necessary configuration units can be added on this basis.

[0047] The backwash device 13 includes a backwash buffer tank 23, a backwash pump 24, and a backwash filter 27. The backwash buffer tank 23 is a cylindrical tank structure. The backwash agent enters the backwash buffer tank 23 through the backwash reflux main pipe 30 and is discharged from the backwash buffer tank 23 through the backwash outlet main pipe 29. The backwash filter 27 is located on the backwash outlet main pipe 29. The backwash outlet main pipe 29 is provided with a backwash reflux valve 25 and a backwash regulating valve 26; the backwash device 13 also includes a backwash pump inlet pipe and a backwash pump outlet pipe. The backwash pump inlet pipe is located at the bottom of the backwash buffer tank 23, and the center line of the backwash pump inlet pipe overlaps with the tank diameter dividing line of the backwash buffer tank 23; the backwash pump outlet pipe is located in the lower middle part of the backwash buffer tank 23, and the center line of the backwash pump outlet pipe overlaps with the tank tangent of the backwash buffer tank 23.

[0048] The backwash device 13 implements the reagent configuration and dissolution process through the backwash pump 24, the backwash reflux valve 25 and related auxiliary pipes (the backwash regulating valve 26 is in a closed state at this time). The backwash device 13 implements the filter unit group backwash process through the backwash pump 24, the backwash regulating valve 26 and related auxiliary pipes (the backwash reflux valve 25 is in a closed state at this time). The backwash filter 27 is located at the backwash outlet main pipe 29. By setting two groups, they are mutually standby and are used to filter and intercept impurity particles mixed in the backwash reagent. The backwash reagent enters the backwash buffer tank 23 through the backwash reflux main pipe 30. The backwash reagent is added through the upper opening of the backwash buffer tank 23. The backwash reagent dilution volume is added through the water replenishment control valve and related pipelines. The liquid level of the backwash buffer tank 23 can be observed and determined by a liquid level meter. The overflow water of the backwash buffer tank 23 is connected to the drain pipe of the backwash buffer tank drain valve 28.

[0049] The backwash device 13 in this embodiment is not only applicable to the backwash operation process of the ion trap 5, but also applicable to the cleaning process of other heat exchanger equipment (such as plate heat exchangers and shell-and-tube heat exchangers) made of different materials or in different forms using similar processes.

[0050] The isolation electric control valve 4 , the front-end pressure transmitter 3 , the rear-end pressure transmitter 6 , the backwash device 13 , the backwash return valve 25 and the backwash regulating valve 26 are respectively connected to the VSD logic control system 9 .

[0051] like Figure 3 As shown, the ion trap 5 is a vertical pressure vessel with an internal lining of glass fiber material anti-corrosion coating, which is used for pre-filtering large impurities and absorbing and replacing corrosive ions in seawater, thereby protecting the seawater desalination aluminum alloy heat exchange tube from corrosion. The ion trap 5 is filled with filter material, and the filter material is an aluminum ring 14 made of the same material as the seawater desalination device heat exchange tube. The aluminum ring 14 of the ion trap 5 can be inspected and replaced by removing the upper end cover of the ion trap 5. The outer diameter of the aluminum ring 14 is 45-65mm, the length is 50-70mm, and the wall thickness is 1.5-2.2mm. The size of the aluminum ring 14 takes into account the surface area of ​​the aluminum ring 14 and the The flux of the flowing water is adapted to avoid the corrosive ions in the seawater from having too little time to contact and react. The wall thickness takes into account the overall operation cycle and regular maintenance cycle of the aluminum ring 14. The filling amount of the aluminum ring 14 inside the ion trap 5 is fully filled. The ion trap drain valve 10 is located at the bottom of the ion trap 5, and is used to discharge the water stored in the ion trap 5 and the backwash wastewater; a partition 15 is provided inside the ion trap 5, and the partition 15 is respectively located between the inlet and outlet ends of the ion trap 5; an ion trap exhaust valve 31 for discharging the gas inside the ion trap 5 is provided at the highest point of the top end cover of the ion trap 5, and is used to discharge the gas inside the ion trap 5 to avoid abnormal vibration during operation and backwashing.

[0052] The structure of the ion trap 5 and the material, size, thickness, etc. of the internal filling material in the present invention can be freely adjusted according to the subsequent equipment protection metal and the water flux of the flow medium. The above is only selected for practical use in this embodiment.

[0053] A backwash inlet valve 16 is provided on the outlet pipe of the ion trap 5, and a backwash outlet valve 17 is provided on the inlet pipe of the ion trap 5. The backwash inlet valve 16 and the backwash outlet valve 17 are respectively connected to the VSD logic control system 9; an ion trap drain valve 10 is provided on the pipe leading to the drain ditch 11 of the ion trap 5, and the filter 7 is arranged at the rear end of the ion trap 5 and a filter drain valve 12 is provided on the pipe leading to the drain ditch 11 of the filter 7, and the ion trap drain valve 10 and the filter drain valve 12 are respectively connected to the VSD logic control system 9.

[0054] The filter 7 is a vertical pressure vessel with an internal lining coated with a glass fiber material anti-corrosion coating, which is used to filter and retain any medium or large solid particles including the above-mentioned ion trap 5 aluminum ring 14 that blocks the spray system of the seawater desalination device. The filter 7 is provided with a filter cartridge 18 inside, and the filter cartridge 18 is composed of a filter screen of an upper column structure and a lower cone structure. The filter screen of the filter 7 can be inspected and replaced by removing the upper end cover of the filter 7. The 316 stainless steel inner lining reinforcement ring is adopted. The thickness of the filter screen is 1.5-2.5mm, the aperture is 2-2.5mm, and the porosity is 42%. The water flux of the filter cartridge 18 of the filter 7 meets 1.05-1.1 times the water demand of the spray system of the seawater desalination device. The filter cartridge 18 is provided with a filter hole adjustment ring 19 outside, and the filter hole adjustment ring 19 and the filter cartridge 18 can slide slightly relative to each other. The filter hole adjustment ring 19 has the same opening as the filter screen. When the filter hole adjustment ring 19 overlaps with the mesh of the filter cartridge 18, the water flux is maximum. When the filter hole adjustment ring 19 and the mesh of the filter cartridge 18 are staggered, the water flux is reduced. It is used to adjust the overlap to facilitate the interception of impurity particles of different diameters. A backwash isolation valve 21 is provided in the upper and middle part of the filter cartridge 18. The backwash isolation valve 21 is connected to the isolation valve actuator through a valve stem, and the isolation valve plate is slightly smaller than the inner wall size of the column filter cartridge 18; a zinc sacrificial anode 20 is provided on the outer wall of the lower part of the filter cartridge 18 to slow down the corrosion rate of the filter screen and extend its service life; a drain pipe is provided at the lowest point of the cone section at the bottom of the filter cartridge 18, and is connected to the drain valve of the filter 7; a filter 7 exhaust valve is also provided at the highest point of the top end cover of the filter 7, which can be used to discharge the internal gas of the filter 7 to avoid abnormal vibration during operation and backwashing.

[0055] The filter structure and the filter cartridge material, form, thickness, pore size, opening rate, etc. of the present invention can be freely adjusted according to specific circumstances, and the above are only selected for practical use in this embodiment.

[0056] Working method:

[0057] The cleaning method of the filter device of the present invention is as follows: S1: According to the monitoring VSD logic control system 9, the pressure difference change feedback signal of the pressure transmitter at the inlet and outlet sides of the pre-filter unit is monitored, and it is determined that the filter unit group in the pre-filter unit needs to be isolated and backwashed;

[0058] S2: The VSD logic control system 9 automatically adjusts the operation state and controls the standby pre-filter unit to start. The specific control method is as follows: After opening the inlet electric control valve 1, the isolation electric control valve 4, and the outlet electric control valve 8, the seawater booster pump 2 is immediately started (at this time, the ion trap drain valve 10, the filter drain valve 12, the backwash inlet valve 16, and the backwash outlet valve 17 are all in the closed state). After the outlet flow rate is maintained stable, a switching completion feedback instruction is issued. At the same time, the backwash operation of the filter 7 in the standby filter unit group is started first, and the backwash of the filter 7 is closed. Backwash isolation valve 21 is opened, and filter drain valve 12 is opened. At this time, the filter medium flows out along the filter cartridge 18 at the front end of the valve plate of backwash isolation valve 21, and then enters the filter cartridge 18 at the rear end of the valve plate of backwash isolation valve 21 from the outside to the inside, and the impurities trapped inside the filter cartridge 18 are stripped and discharged along the filter drain valve 12. When the turbidity of the backwash drainage is detected to be lower than the set value, the backwash operation of the filter 7 is stopped, and the pre-filter unit that needs to be isolated and stopped is shut down (at this time, the inlet electric control valve 1, the isolation electric control valve 4, and the outlet electric control valve 8 seawater booster pump 2 are all in a closed or stopped state);

[0059] S3: The ion trap 5 in the idle filter unit group is backwashed and purified by the VSD logic control system 9. The specific control method is as follows: start the backwash control process of the backwash device 13, start the backwash pump 24, open the backwash regulating valve 26, the backwash inlet valve 16, and the backwash outlet valve 17 (at this time, the ion trap drain valve 10, the filter drain valve 12, and the backwash reflux valve 25 are in a closed state) to perform a backwash reagent circulation cleaning process, and by regularly detecting the reagent concentration and turbidity, appropriately discharge and replenish the backwash reagent, wait until the backwash reagent concentration remains constant for a period of time, stop the backwash operation of the ion trap 5, open the ion trap drain valve 10 and the filter drain valve 12, and close the backwash inlet valve 16 and the backwash outlet valve 17, and stop the backwash device 13.

[0060] The logic control system of the present invention performs feedback adjustment based on the pressure difference change monitored by the pressure transmitter at the inlet and outlet sides of the filter unit, and can also perform feedback adjustment based on other monitoring signals. The backwashing operation process at least ensures that the electric regulating valve, the drain valve and the pressure transmitter, and the backwashing device 13 are respectively controllably connected to the logic control system. The logic control program of this embodiment is only selected for on-site economic and practical conditions, and other control programs can also be used.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pre-filter device for an aluminum heat exchange tube type seawater desalination system, characterized in that: A pre-filter device is arranged at the cold source side inlet of the low-temperature multi-effect seawater desalination system, wherein the pre-filter device comprises a plurality of pre-filter units, and the plurality of pre-filter units are arranged in a mother pipe split form; The pre-filter unit includes a seawater booster pump, a front-end pressure transmitter, an ion trap, a rear-end pressure transmitter, a filter, a VSD logic control system and a backwash device. The ion trap is connected to the filter. A filter exhaust valve is also provided at the highest point of the top end cover of the filter to discharge the gas inside the filter. An isolation electric control valve is provided on the pipeline connecting the seawater booster pump to the ion trap. The backwash device is connected to the inlet and outlet pipe sections of the ion trap through a pipeline. The backwash device comprises a backwash buffer tank, a backwash pump, and a backwash filter. The backwash agent enters the backwash buffer tank through a backwash reflux main pipe and is discharged from the backwash buffer tank through a backwash outlet main pipe. The backwash filter is located on the backwash outlet main pipe, and a backwash reflux valve and a backwash regulating valve are provided on the backwash outlet main pipe. The isolation electric control valve, the front-end pressure transmitter, the rear-end pressure transmitter, the backwash device, the backwash reflux valve and the backwash regulating valve are respectively connected to the VSD logic control system; The ion trap is a vertical pressure vessel with an internal lining and anti-corrosion coating of glass fiber material. The ion trap is filled with filter material, which is an aluminum ring made of the same material as the heat exchange tube of the seawater desalination device. The outer diameter of the aluminum ring is 45-65mm, the length is 50-70mm, and the wall thickness is 1.5-2.2mm. The ion trap is provided with a partition, which is respectively located between the inlet end and the outlet end of the ion trap. The highest point of the top end cover of the ion trap is provided with an ion trap exhaust valve for discharging the gas inside the ion trap.

2. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 1 is characterized in that: An ion trap drain valve is provided on the pipeline leading to the drain ditch from the ion trap, the filter is arranged at the rear end of the ion trap and a filter drain valve is provided on the pipeline leading to the drain ditch from the filter, and the ion trap drain valve and the filter drain valve are respectively connected to the VSD logic control system.

3. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 1, characterized in that: A backwash inlet valve is provided on the pipeline at the outlet end of the ion trap, and a backwash outlet valve is provided on the pipeline at the inlet end of the ion trap. The backwash inlet valve and the backwash outlet valve are respectively connected to the VSD logic control system.

4. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 1, characterized in that: The filter is a vertical pressure vessel with an internal lining and an anti-corrosion coating of glass fiber. A filter cartridge is provided inside the filter. The filter cartridge consists of a filter screen with an upper cylindrical structure and a lower conical structure. The filter screen has a thickness of 1.5-2.5 mm, an opening diameter of 2-2.5 mm, and an opening rate of 42%. A filter hole adjustment ring is provided on the outside of the filter cartridge. A backwash isolation valve is provided in the upper and middle part of the filter cartridge, and the backwash isolation valve is connected to the isolation valve actuator through a valve stem; a zinc sacrificial anode is provided on the lower outer wall of the filter cartridge; a drain pipe is provided at the lowest point of the cone section at the bottom of the filter cartridge, and is connected to the filter drain valve.

5. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 1, characterized in that: The outlet end of the filter is provided with an outlet electric control valve, the front end pressure transmitter is located in the pipe section in front of the isolation electric control valve, and the rear end pressure transmitter is located in the pipe section in front of the outlet electric control valve of the filter.

6. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 1, characterized in that: The backwash device also includes a backwash pump inlet pipe and a backwash pump outlet pipe. The backwash pump inlet pipe is located at the bottom of the backwash buffer tank, and the backwash pump outlet pipe is located at the lower middle part of the backwash buffer tank.

7. The aluminum heat exchange tube type seawater desalination system pre-filter device according to claim 6, characterized in that: The center line of the backwash pump inlet pipe overlaps with the tank body diameter dividing line of the backwash buffer tank, and the center line of the backwash pump outlet pipe overlaps with the tank body tangent line of the backwash buffer tank.

8. A method for cleaning a pre-filter device of an aluminum heat exchange tube desalination system according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: According to the monitoring VSD logic control system, the pressure difference change feedback signal of the pressure transmitter on the inlet and outlet sides of the pre-filter unit is monitored, and it is determined that the filter unit group in the pre-filter unit needs to be isolated and backwashed; S2: The VSD logic control system implements automatic adjustment of the operating state and controls the start-up of the standby pre-filter unit. The specific control method is as follows: After opening the inlet electric control valve, the isolation electric control valve, and the outlet electric control valve, the seawater booster pump is immediately started. At this time, the ion trap drain valve, the filter drain valve, the backwash inlet valve, and the backwash outlet valve are all in a closed state. After the outlet flow is maintained stable, a switching completion feedback instruction is issued. At the same time, the backwash operation of the filter in the standby filter unit group is first started and the filter backwash isolation valve is closed, and the filter drain valve is opened. At this time, the filter medium flows out along the filter cartridge at the front end of the backwash isolation valve plate, and then enters the filter cartridge at the rear end of the backwash isolation valve plate from the outside to the inside, and the impurities trapped in the filter cartridge are stripped and discharged along the filter drain valve. When the turbidity of the backwash drainage is detected to be lower than the set value, the filter backwash operation is stopped, and the pre-filter unit that needs to be isolated and stopped is shut down. At this time, the inlet electric control valve, the isolation electric control valve, and the seawater booster pump of the outlet electric control valve are all in a closed or stopped state; S3: Implement backwash purification operation on the ion trap in the idle filter unit group through the VSD logic control system. The specific control method is as follows: start the backwash control process of the backwash device, start the backwash pump, open the backwash regulating valve, the backwash inlet valve, and the backwash outlet valve to carry out the backwash reagent circulation cleaning process. At this time, the ion trap drain valve, the filter drain valve, and the backwash reflux valve are in a closed state, and the reagent concentration and turbidity are regularly tested to appropriately discharge and replenish the backwash reagent. When the backwash reagent concentration remains constant for a period of time, stop the ion trap backwash operation, open the ion trap drain valve and the filter drain valve, and close the backwash inlet valve and the backwash outlet valve, and stop the backwash device.

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