Mvr coupling multi-effect rectification imidacloprid wastewater resource recycling method and device

Abstract

The application discloses a kind of MVR coupling multi-effect rectification imidacloprid wastewater resource recovery method and device, including light tower, heavy tower, rectification tower, MVR compressor, MVR falling film reboiler and MVR distilled water tank, after heating, the pesticide wastewater raw material liquid from production workshop enters light tower, after decompression separation in light tower, light component material dichloroethane and methanol obtained at the top of light tower are pumped to plant area recovery system;After light removal by light tower, the liquid is pumped to heavy tower heating and is separated by flash evaporation;Heavy tower produces water vapor, after compression, the enthalpy is increased, and then it is used as heat source to return to the reboiler of heavy tower to heat the circulating liquid, after distillation and concentration, the heavy component liquid is pumped into the rectification tower and is distilled under reduced pressure, after rectification, DMF and a small part of water vapor are pumped to plant area recovery system production line for reuse, and the remaining mother liquor enriched imidazolidine is recovered after cooling.The device can reduce the heat transfer end difference, reduce energy consumption, and realize multi-effect rectification pesticide production wastewater resource recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide production wastewater resource recovery equipment, and in particular to an MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method and device. Background Art

[0002] my country is a major global pesticide producer. Pollution from the pesticide industry primarily comes from wastewater discharged during the production process. In 2020, the national pesticide industry discharged approximately 250 million tons of wastewater annually, primarily from drainage during production, product washing water, and equipment and workshop floor cleaning water. Pesticide production wastewater has long been a focus of public attention due to its high toxicity, high concentration, and difficulty in treatment. Pesticide production wastewater treatment technologies can be categorized into physicochemical, chemical, biochemical, and incineration methods based on the principles employed. Extraction and distillation are the most widely used physicochemical methods for treating pesticide production wastewater. Since extraction requires solvents, solvent recovery combined with distillation is an effective way to avoid secondary solvent contamination and facilitate resource reuse of pesticide production wastewater. However, distillation is energy-intensive and has high treatment costs. Existing multi-effect distillation equipment has complex structures, lengthy process flows, low resource utilization, and high equipment and labor costs. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method and device for resource recovery of imidacloprid wastewater by MVR coupling multi-effect distillation.

[0004] The present invention is achieved through the following technical solution: a method for resource recovery of imidacloprid wastewater by MVR coupling multi-effect distillation, wherein the method comprises a light removal tower, a heavy removal tower, a distillation tower, an MVR compressor, an MVR falling film reboiler and an MVR distilled water tank, and the resource recovery method comprises the following steps:

[0005] Step 1: The pesticide wastewater raw liquid from the production workshop is heated and then enters the light component removal tower. After decompression and separation in the light component removal tower, the light component substances dichloroethane and methanol obtained at the top of the light component removal tower are pumped to the factory recovery system; the non-condensable gas in the light component removal tower is extracted and discharged to the workshop exhaust gas treatment system by a vacuum pump;

[0006] Step 2: The liquid after light removal in the de-lightening tower is pumped to the de-weighting tower for heating and flash separation. The water vapor enters the MVR compressor for compression to increase enthalpy and temperature, then enters the MVR falling film reboiler shell side to release the latent heat of condensation and is collected in the MVR distilled water tank; the liquid after flash evaporation in the de-weighting tower and the circulating liquid are pumped together through the falling film circulation pump to the MVR falling film reboiler tube side, absorb the latent heat released by the shell side steam and then flow back to the de-weighting tower; the distilled water collected in the distilled water tank is pumped to the distilled water stock heater to further release some sensible heat, and then returned to the washing workshop for reuse after cooling;

[0007] Step 3: The deweighting tower extracts the liquid containing imidazolidine and DMF, which is then pumped to the distillation tower for vacuum distillation after distillation. After distillation, DMF and a small amount of water vapor are evaporated and pumped to the plant recovery system production line for application. The remaining imidazolidine-rich mother liquor is cooled to recover the imidazolidine and return it to the production line for application.

[0008] A device for realizing a method for resource recovery of imidacloprid wastewater by MVR coupling multi-effect distillation, the device comprises a raw liquid tank, a secondary raw liquid heater, a raw liquid pump, a light removal condenser, a light removal tank, a light removal reboiler, a light removal circulation pump, a light removal feed liquid pump and a light removal extraction pump; the raw liquid tank and the secondary raw liquid heater are arranged in front of the light removal tower, and the heat sources of the secondary raw liquid heater come from the recovered MVR distilled water and the sensible heat of the condensed water of the light removal tower and the distillation tower respectively; the secondary raw liquid heater comprises a distilled water raw liquid heater and a condensed water raw liquid heater connected thereto; the raw liquid tank inlet is connected to the raw liquid from the production workshop through a connecting pipe, the raw liquid pump inlet is connected to the raw liquid tank, and the raw liquid pump outlet is connected to the distilled water raw liquid heater; the top of the light removal tower is connected to the light removal condenser The condenser and the de-lightening tank are connected respectively, the bottom of the de-lightening tower is connected to the bottom pipe side of the de-lightening reboiler through the de-lightening circulation pump, and the upper pipe side of the de-lightening reboiler is connected to the lower part of the de-lightening tower; the de-lightening condenser and the de-lightening tank are also connected to a de-lightening vacuum pump for extracting non-condensable gas in the de-lightening tower; the bottom of the de-lightening tank is connected to the plant recovery system through the de-lightening extraction pump; the bottom of the de-lightening tower is connected to the de-heavy tower through the de-lightening liquid pump; the heat source of the de-lightening reboiler comes from the plant heating steam, and the de-lightening reboiler is connected to the condensate raw liquid heater through the second condensate recovery interface, the heating steam goes through the shell side, and after releasing the latent heat, it is connected to the condensate raw liquid heater through the second condensate recovery interface, and is further released in the condensate raw liquid heater before recycling. The light components evaporated from the top of the light-removal tower are condensed in the light-removal condenser, part of which flows back to the light-removal tower, and the other part enters the light-removal tank for recovery; there is a light-removal reboiler at the bottom of the light-removal tower, and the heat source comes from the heating steam of the plant area. The heating steam goes through the shell side, and after releasing the latent heat, it is sent to the condensate raw liquid heater through the second condensate recovery interface, and after further releasing the sensible heat, it returns to the plant area condensate collection system; a discharge pump (light-removal liquid pump) is provided at the bottom of the light-removal tower to extract hot water containing DMF and imidazolidine to the heavy-removal tower.

[0009] The device also includes a falling film circulation pump, a deweighting liquid pump, a distilled water reflux pump, a distilled water recovery pump and a first condensed water recovery interface; the top of the deweighting tower is connected to the MVR compressor, and the MVR compressor is connected to the upper shell side of the MVR falling film reboiler; the bottom tube side of the MVR falling film reboiler is connected to the lower part of the deweighting tower, and the top of the MVR falling film reboiler tube side is connected to the bottom of the deweighting tower through the falling film circulation pump; the bottom of the MVR falling film reboiler shell side is connected to the MVR distilled water tank, and the outlet of the MVR distilled water tank is connected to the distilled water stock liquid heater in sequence through the distilled water recovery pump and the first condensed water recovery interface, and the outlet of the MVR distilled water tank is also connected to the upper part of the deweighting tower through the distilled water reflux pump; the bottom of the deweighting tower is connected to the distillation tower through the deweighting liquid pump. The steam from the top of the de-weighting tower first enters the MVR compressor, and after increasing enthalpy and heating, it enters the shell side of the MVR falling film reboiler at the bottom of the tower, and then enters the MVR distilled water tank after releasing latent heat; a falling film circulation pump is provided at the bottom of the de-weighting tower to pump the material into the MVR falling film reboiler, and after falling film heating in the heater tube, it flows back to the de-weighting tower; the MVR distilled water tank collects the condensed water from the MVR falling film reboiler, part of which flows back to the top of the de-weighting tower, and the other part is pumped to the distilled water raw liquid heater, and then returns to the production water washing station for circulation after further releasing sensible heat; a de-weighting liquid pump is also provided at the bottom of the de-weighting tower to pump the mother liquor rich in imidazolidine and DMF to the distillation tower.

[0010] The device also includes a distillation condenser, a concentration separation tank, a distillation reboiler, a DMF concentrate extraction pump, an imidazolidine concentrate extraction pump, a forced circulation pump and a distillation vacuum pump; the top outlet of the distillation tower is connected to the distillation condenser, the concentration separation tank is connected to the upper inlet of the distillation tower, and one outlet of the distillation condenser is connected to the connecting pipeline between the concentration separation tank and the distillation tower through a connecting pipe; the concentration separation tank and the distillation condenser are connected to the distillation vacuum pump in parallel, and are connected to the workshop exhaust gas treatment system through the distillation vacuum pump. The bottom of the concentration separation tank is connected to the plant recovery system through the DMF-rich DMF concentrate extraction pump; the bottom of the distillation tower is connected to the bottom pipe side of the distillation reboiler through the forced circulation pump, the top of the distillation reboiler pipe side is connected to the lower part of the distillation tower, and the lower shell side of the distillation reboiler is connected to the condensate raw liquid heater through the second condensate recovery interface. The heat source of the distillation reboiler comes from the plant heating steam and enters the distillation reboiler shell side; the bottom of the distillation tower is sent back to the production line for use through the imidazolidine concentrate extraction pump. A portion of the DMF-rich condensate condensed from the distillation condenser at the top of the distillation tower is refluxed back to the distillation tower, and the other portion enters the concentration separation tank for recycling and reuse; a distillation reboiler is provided at the bottom of the distillation tower, and the heat source comes from the heating steam of the plant area. The second condensate recovery interface is sent to the condensate raw liquid heater, which returns to the plant area condensate collection system after releasing the sensible heat; a discharge pump (imidazole concentrate extraction pump) is provided at the bottom of the distillation tower to extract the imidazolidine-rich concentrate and pump it back to the production line for reuse.

[0011] The MVR falling film reboiler adopts twisted elliptical tubes as the heater heat exchange tube bundle. A guide tube for wrapping the heat exchange tube bundle is provided in the cylinder of the MVR falling film reboiler.

[0012] The light removal reboiler and the rectification reboiler both adopt heat exchange tube bundles with twisted elliptical tubes arranged in parallel; the distilled water stock heater and the condensed water stock heater adopt twisted elliptical tube shell and tube heat exchangers or plate heat exchangers.

[0013] The light removal tower and the heavy removal tower both adopt a plate tower structure, and the distillation tower adopts a plate tower structure or a packed tower structure.

[0014] The heat exchange tube bundles in shell-and-tube heaters and reboilers are constructed from a number of high-surface-area twisted elliptical tubes, bundled together to create convex contact points between the tubes, creating a mutually supported structure. This creates axial multi-channel flow paths, eliminating the need for baffles or intermediate support tubesheets. The twisted elliptical tubes have a nearly elliptical cross-section, twisted to form a helical structure through secondary processing. This three-dimensional, variable-space, turbulent flow design creates axial multi-channel paths between the tube bundles, minimizing heat exchange end differences, reducing energy loss, and improving heat exchange efficiency.

[0015] Compared with the prior art, the advantages of the present invention are as follows: the device utilizes the latent heat of the steam produced by the de-weighting tower as the heat source for the de-weighting reboiler. Since the heat consumption of the de-weighting tower accounts for more than 80% of the entire multi-effect distillation system, the steam produced by the de-weighting tower is heated by the MVR device to increase the enthalpy and heat it for reboiling at the bottom of the tower. This can greatly reduce the energy consumption of the de-weighting tower, avoid the use of a top condenser to cool and recover distilled water, and thus reduce the energy and water consumption of the cooling system, achieving energy and water conservation in the process of resource recovery of pesticide production wastewater. The energy transfer equipment or device of the multi-effect distillation system is optimized and designed in combination with the three-dimensional variable space turbulent flow design method, which can reduce the heat exchange end difference of the energy transfer equipment, reduce the power consumption of the energy transfer system, further reduce the energy consumption of the multi-effect distillation system, and achieve low-carbon operation of the multi-effect distillation pesticide production wastewater resource recovery system. The operating reliability and heat exchange performance of the reboiler with a mutually supporting structure without baffles are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of a partial structure of a heat exchange tube bundle using twisted elliptical tubes according to an embodiment of the present invention;

[0018] Figure 3 This is a cross-sectional view taken along the cross-sectional direction when the heat exchange tube bundle according to an embodiment of the present invention uses twisted elliptical tubes.

[0019] The meanings of the reference numerals in the figure are as follows: 1. Raw liquid tank; 2. Distilled water raw liquid heater; 3. Condensed water raw liquid heater; 4. Light removal tower; 5. Light removal condenser; 6. Light removal tank; 7. Light removal reboiler; 8. Heavy removal tower; 9. MVR compressor; 10. MVR falling film reboiler; 11. MVR distilled water tank; 12. Distillation tower; 13. Distillation condenser; 14. Concentration separation tank; 15. Distillation reboiler; 161. Raw liquid pump; 162. Light removal circulation pump; 163. Light removal feed liquid pump; 164. Light removal extraction pump; 165. Membrane circulation pump; 166, deheaving liquid pump; 167, distilled water reflux pump; 168, distilled water recovery pump; 169, imidazolidine concentrate production pump; 1610, DMF concentrate production pump; 1611, forced circulation pump; 171, deheaving vacuum pump; 172, distillation vacuum pump; 181, first condensate recovery interface; 182, second condensate recovery interface; A, raw material liquid; B, non-condensable gas; C, plant heating steam; D, plant recovery system; E, cooling system; F, production water washing station; G, plant condensate collection system. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example

[0022] See Figure 1 , which is a MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method, the method includes a light removal tower 4, a heavy removal tower 8, a distillation tower 12, an MVR compressor 9, an MVR falling film reboiler 10 and an MVR distilled water tank 11, and the resource recovery method includes the following steps:

[0023] Step 1: The pesticide wastewater raw liquid from the production workshop is heated and then enters the light component removal tower 4. After decompression and separation in the light component removal tower 4, the light component substances dichloroethane and methanol obtained at the top of the light component removal tower 4 are pumped to the factory recovery system D; the non-condensable gas B in the light component removal tower 4 is extracted and discharged to the workshop exhaust gas treatment system by a vacuum pump;

[0024] Step 2: The liquid after light removal in the light removal tower 4 is pumped to the de-weighting tower 8 for heating and flash separation. The water vapor enters the MVR compressor 9 for compression to increase enthalpy and temperature, then enters the MVR falling film reboiler 10 shell side to release latent heat of condensation and then is collected in the MVR distilled water tank 11; the liquid after flash evaporation in the de-weighting tower 8 and the circulating liquid are pumped together through the falling film circulation pump 165 to the MVR falling film reboiler 10 tube side, absorb the latent heat released by the shell side steam, and then flow back to the de-weighting tower; the distilled water collected in the distilled water tank is pumped to the distilled water stock heater 2 to further release part of the sensible heat, and then returned to the washing workshop for reuse after cooling;

[0025] Step 3: A portion of the liquid rich in imidazolidine and DMF is extracted from the bottom of the deweighting tower 8, and after distillation, it is pumped to the distillation tower 12 for vacuum distillation. After distillation, DMF and a small amount of water vapor are evaporated and pumped to the plant recovery system D production line for application. The remaining mother liquor rich in imidazolidine is cooled to recover the imidazolidine and return it to the production line for application.

[0026] This recovery method aims to utilize the solubility differences of the imidazolidine dissolved in the dichloroethane solution of imidacloprid to dissolve the imidazolidine in hot water. The hot water after dissolving the imidazolidine contains impurities such as DMF, dichloroethane, and methanol. DMF and imidazolidine are recovered using a multi-stage distillation process. Light components such as dichloroethane and methanol are removed at the top of a light removal tower 4. Hot water containing DMF and imidazolidine is extracted from the bottom of the light removal tower 4 and then sent to a heavy removal tower 8. In the heavy removal tower 8, an MVR distillation method is used. The steam extracted from the top of the tower passes through an MVR compressor 9 to increase enthalpy before returning to the MVR falling film reboiler 10 at the bottom of the tower to release latent heat and reboil at the bottom. The distilled water then enters the raw liquid heater to further release latent heat before being recycled back to the production water washing station F. A mother liquor containing imidazolidine and DMF is extracted from the bottom of the heavy removal tower 8. DMF is distilled off after rectification and then reused in the production line. The remaining mother liquor is cooled, and the imidazolidine is recovered and returned to the production line.

[0027] A device for realizing a method for resource recovery of imidacloprid wastewater by MVR coupling multi-effect distillation, the device comprises a raw liquid tank 1, a secondary raw liquid heater, a raw liquid pump 161, a light removal condenser 5, a light removal tank 6, a light removal reboiler 7, a light removal circulation pump 162, a light removal feed liquid pump 163 and a light removal extraction pump 164; a raw liquid tank 1 and a secondary raw liquid heater are provided in front of the light removal tower 4, and the heat sources of the secondary raw liquid heater come from the recovered MVR distilled water and the sensible heat of the condensed water of the light removal tower 4 and the distillation tower 12 respectively; the secondary raw liquid heater comprises a distilled water raw liquid heater 2 and a condensed water raw liquid heater 3 connected thereto; the inlet of the raw liquid tank 1 is connected to the raw material liquid A from the production workshop through a connecting pipe, the inlet of the raw liquid pump 161 is connected to the raw liquid tank 1, and the outlet of the raw liquid pump 161 is connected to the distilled water raw liquid heater 2; the top of the light removal tower 4 is connected to the light removal tower 4. The condenser 5 and the de-lightening tank 6 are connected separately, the bottom of the de-lightening tower 4 is connected to the bottom pipe side of the de-lightening reboiler 7 through the de-lightening circulation pump 162, and the upper pipe side of the de-lightening reboiler 7 is connected to the lower part of the de-lightening tower 4; the de-lightening condenser 5 and the de-lightening tank 6 are also connected to a de-lightening vacuum pump 171 for extracting the non-condensable gas B in the de-lightening tower 4; the bottom of the de-lightening tank 6 is connected to the plant recovery system D through the de-lightening extraction pump 164; the bottom of the de-lightening tower 4 is connected to the de-heavy tower 8 through the de-lightening liquid pump 163; the heat source of the de-lightening reboiler 7 comes from the plant heating steam C, and the de-lightening reboiler 7 is connected to the condensate raw liquid heater 3 through the second condensate recovery interface 182; the heating steam goes through the shell side, and after releasing the latent heat, it is connected to the condensate raw liquid heater 3 through the second condensate recovery interface 182, and is further released in the condensate raw liquid heater 3 before being recycled. The light components evaporated from the top of the light removal tower 4 are condensed in the light removal condenser 5, a part of which flows back to the light removal tower 4, and the other part enters the light removal tank 6 and is recovered; there is a light removal reboiler 7 at the bottom of the light removal tower 4, and the heat source comes from the plant heating steam C. The heating steam goes through the shell side, releases the latent heat, and is sent to the condensate raw liquid heater 3 through the second condensate recovery interface 182. After further releasing the sensible heat, it returns to the plant condensate collection system G; a discharge pump (light removal liquid pump 163) is provided at the bottom of the light removal tower 4 to extract hot water containing DMF and imidazolidine to the heavy removal tower 8. In this embodiment, the setting of the light removal vacuum pump 171 ensures the vacuum operation of the system while extracting the non-condensable gas from the light removal tower 4.

[0028] The device also includes a falling film circulation pump 165, a deweighting liquid pump 166, a distilled water reflux pump 167, a distilled water recovery pump 168 and a first condensed water recovery interface 181; the top of the deweighting tower 8 is connected to the MVR compressor 9, and the MVR compressor 9 is connected to the upper shell side of the MVR falling film reboiler 10; the bottom tube side of the MVR falling film reboiler 10 is connected to the lower part of the deweighting tower 8, and the top of the MVR falling film reboiler 10 tube side is connected to the bottom of the deweighting tower 8 through the falling film circulation pump 165; the bottom of the shell side of the MVR falling film reboiler 10 is connected to the MVR distilled water tank 11, and the outlet of the MVR distilled water tank 11 is connected to the distilled water stock heater 2 in sequence through the distilled water recovery pump 168 and the first condensed water recovery interface 181, and the outlet of the MVR distilled water tank 11 is also connected to the upper part of the deweighting tower 8 through the distilled water reflux pump 167; the bottom of the deweighting tower 8 is connected to the distillation tower 12 through the deweighting liquid pump 166. The steam from the top of the de-weighting tower 8 first enters the MVR compressor 9, and after increasing enthalpy and heating, enters the shell side of the MVR falling film reboiler 10 at the bottom of the tower, releases latent heat, and then enters the MVR distilled water tank 11; a falling film circulation pump 165 is provided at the bottom of the de-weighting tower 8 to pump the material into the MVR falling film reboiler 10, and after falling film heating in the heater tube, it refluxes to the de-weighting tower 8; the MVR distilled water tank 11 collects the condensed water from the MVR falling film reboiler 10, part of which is refluxed to the top of the de-weighting tower 8, and the other part is pumped to the distilled water raw liquid heater 2, further releases sensible heat, and then returns to the production water washing station F for recycling; a de-weighting liquid pump 166 is also provided at the bottom of the de-weighting tower 8 to pump the mother liquor rich in imidazolidine and DMF to the distillation tower 12.

[0029] The device also includes a distillation condenser 13, a concentration separation tank 14, a distillation reboiler 15, a DMF concentrate extraction pump 1610, an imidazolidine concentrate extraction pump 169, a forced circulation pump 1611 and a distillation vacuum pump 172; the top outlet of the distillation tower 12 is connected to the distillation condenser 13, the concentration separation tank 14 is connected to the upper inlet of the distillation tower 12, and one outlet of the distillation condenser 13 is connected to the connecting pipeline between the concentration separation tank 14 and the distillation tower 12 through a connecting pipe; the concentration separation tank 14 and the distillation condenser 13 are connected to the distillation vacuum pump 172 in parallel, and are connected to the workshop through the distillation vacuum pump 172. The exhaust gas treatment system is connected; the bottom of the concentration separation tank 14 is connected to the plant recovery system D through the DMF concentrate extraction pump 1610; the bottom of the distillation tower 12 is connected to the bottom pipe side of the distillation reboiler 15 through the forced circulation pump 1611, the top of the distillation reboiler 15 pipe side is connected to the lower part of the distillation tower 12, and the lower shell side of the distillation reboiler 15 is connected to the condensate stock heater 3 through the second condensate recovery interface 182. The heat source of the distillation reboiler 15 comes from the plant heating steam C and enters the distillation reboiler 15 shell side; the bottom of the distillation tower 12 is sent back to the production line for application through the imidazolidine concentrate extraction pump 169. A portion of the DMF vapor evaporated from the rectifying condenser 13 at the top of the rectifying tower 12 is refluxed back to the rectifying tower 12, and the other portion enters the concentration separation tank 14 for recycling. A rectifying reboiler 15 is provided at the bottom of the rectifying tower 12, and its heat source comes from the factory heating steam. A second condensate recovery interface 182 is delivered to the condensate stock heater 3, which releases sensible heat and returns to the factory condensate collection system G. A discharge pump (imidazole concentrate extraction pump 169) is provided at the bottom of the rectifying tower 12 to extract the imidazolidine-rich concentrate and pump it back to the production line for reuse. In this embodiment, the provision of the distillation vacuum pump 172 ensures that the system operates in vacuum while extracting the non-condensable gases from the rectifying tower 12.

[0030] In this embodiment, the raw material liquid A from the production workshop (in this case, the wastewater from the washing process of imidacloprid production) first passes through the raw liquid tank 1, and is then sent to the distilled water raw liquid heater 2 by the raw liquid pump 161. After heating, it continues to enter the condensed water raw liquid heater 3 for secondary heating, and then enters the de-light tower 4. After entering the de-light tower 4, the heated raw material liquid A enters the de-light tower 4 together with the feed liquid in the de-light tower 4 under the action of the de-light tower circulation pump 162. After being heated, it returns to the de-light tower 4. At this time, the high-temperature feed liquid enters the de-light tower 4 and is decompressed and separated. Light components such as dichloroethane and methanol evaporate, and at the same time, some water vapor is contained. It enters the top de-light condenser 5 and the de-light tank 6 for separation. At the same time, part of the condensate refluxes to the top of the de-light tower 4; the non-condensable gas of the de-light system is extracted and discharged to the workshop exhaust gas treatment system by the de-light vacuum pump 171. The bottom of the de-light tank 6 is connected to the de-light tower 4 de-light extraction pump 164, which pumps the extracted light components to the plant recovery system D.

[0031] The light-removal liquid pump 163 at the bottom of the light-removal tower 4 pumps the light-removal liquid to the de-weighting tower 8. After the liquid enters the de-weighting tower 8, part of the water evaporates, and the rest enters the distillation section and is pumped to the top of the MVR falling film reboiler 10 by the falling film circulation pump 165. After being heated by the falling film on the tube side, it returns to the lower part of the de-weighting tower 8; the heated liquid enters the de-weighting tower 8 and is flash-evaporated and separated, wherein the water vapor enters the MVR compressor 9 from the top of the tower, is compressed to increase the enthalpy and heat, and then enters the shell side of the MVR falling film reboiler 10, releases latent heat and condenses, and after the distilled water enters the MVR distilled water tank 11, a part of it is pumped to the distilled water raw liquid heater 2 by the distilled water recovery pump 168, further releases part of the sensible heat and cools down, and then returns to the water washing workshop for reuse; the other part is pumped back to the top of the de-weighting tower 8 by the distilled water reflux pump 167.

[0032] The de-heavy liquid pump 166 at the bottom of the light and heavy tower pumps the distilled liquid to the distillation tower 12. After entering the distillation tower 12, the liquid enters the forced circulation pump 1611 together with the circulating liquid. The liquid is pumped into the distillation reboiler 15 by the forced circulation pump 1611, and returns to the distillation tower 12 after being heated. At this time, the high-temperature liquid enters the distillation tower 12 and is vacuum-distilled. DMF and part of the water vapor enter the distillation condenser 13 and the concentration separation tank 14. At the same time, part of the condensate refluxes to the top of the distillation tower 12; the non-condensable gas of the de-light system is extracted and discharged to the workshop waste gas treatment system by the de-light vacuum pump 171, and the bottom of the concentration separation tank 14 is connected to the DMF concentrate extraction pump 1610 to pump the extracted DMF concentrate to the plant recovery system D; an imidazole concentrate extraction pump 169 is provided at the bottom of the distillation tower 12 to pump the liquid after removing DMF to the water washing workshop for reuse.

[0033] The present embodiment provides a method for resource recovery of wastewater from the washing process of imidacloprid production using MVR-coupled multi-effect distillation. The purpose is to develop a method technology for resource recovery of pesticide production wastewater using multi-effect distillation coupled with an MVR heat pump, and in combination with the design method of three-dimensional turbulent flow heat exchange equipment, maximize the use of waste heat from the multi-effect distillation process, improve the energy utilization level of resource recovery of pesticide production wastewater using multi-effect distillation, thereby greatly reducing the energy cost of wastewater resource recovery; the design method of three-dimensional turbulent flow heat exchange equipment is used to optimize the design of the heat exchange equipment or device of the multi-effect distillation system, and combined with the twisted elliptical tube self-supporting structure design and parallel flow heat exchange form, the heat exchange end difference can be minimized to the maximum extent, the heat exchange efficiency of the heat exchange device can be improved, and the operation reliability of the heat exchange device can be improved.

[0034] The MVR coupled multi-effect distillation imidacloprid production washing process wastewater resource recovery method of this embodiment, compared with the distillation system represented by multi-effect distillation or single-effect MVR heat pump distillation, adopts a heat exchange device with a three-dimensional turbulent flow design and optimization method, which can reduce the heat exchange temperature and pressure of the MVR heat exchange device, reduce the MVR compression power consumption, maximize the use of the waste heat resources of the distillation system, and greatly improve the energy level of wastewater resource recovery. Taking this embodiment as an example, after adopting the MVR coupled multi-effect distillation imidacloprid production washing process wastewater resource recovery process, the unit imidazolidine recovery energy consumption is reduced by more than 75% compared with the traditional single-effect distillation system; compared with the traditional triple-effect distillation imidacloprid production washing process wastewater resource recovery process, the unit imidazolidine recovery energy consumption is reduced by 30% to 50%; in addition, due to the use of MVR technology, no produced water condenser is required, which greatly reduces the energy consumption and water consumption of the cooling system. Therefore, this embodiment can effectively reduce the energy consumption of wastewater resource recovery in the imidacloprid production washing process and realize low-carbon resource recovery of pesticide wastewater.

[0035] In this embodiment, the light-removal condenser 5 and the rectification condenser 13 are both connected to the cooling system E.

[0036] The MVR falling film reboiler 10 uses twisted elliptical tubes as the heater heat exchange tube bundle. A guide tube for wrapping the heat exchange tube bundle is provided in the cylinder of the MVR falling film reboiler 10 .

[0037] The light removal reboiler 7 and the distillation reboiler 15 both use heat exchange tube bundles with twisted elliptical tubes arranged in parallel; the distilled water raw liquid heater 2 and the condensed water raw liquid heater 3 use twisted elliptical tube shell and tube heat exchangers or plate heat exchangers.

[0038] The light-removal tower 4 and the heavy-removal tower 8 both adopt a plate tower structure, and the distillation tower 12 adopts a plate tower structure or a packed tower structure.

[0039] The heat exchange tube bundles of the shell-and-tube heater and reboiler are composed of several high-surface-weight twisted elliptical tubes, bundled together to form a mutually supported structure with convex contact points between the tube bundles. This creates an axial multi-channel flow path, eliminating the need for baffles or intermediate support tube sheets. The twisted elliptical tubes have a nearly elliptical cross-section, twisted to form a spiral structure through secondary processing. The three-dimensional variable space turbulent flow design, which creates axial multi-channels between the heat exchange tube bundles, can reduce heat exchange end differences, reduce energy loss, and improve heat exchange efficiency. The heat exchange tube bundles utilize high-surface-weight twisted elliptical tubes, which are mutually supported by convex contact points to form a stable structure, resulting in excellent heat exchange and facilitating heat recovery. The three-dimensional variable space turbulent flow design, which creates axial multi-channels between the heat exchange tube bundles, and the twisted elliptical tubes' nearly elliptical cross-section design ensures a dead-angle-free flow within the three-dimensional variable space, eliminating vortex points, wear angles, and the formation of scaling and dust accumulation.

[0040] For the use of heat exchange tubes, see Figures 2 to 3 , Figure 2 Only a single twisted elliptical tube is shown. If multiple twisted elliptical tubes are arranged in parallel, support is formed between adjacent twisted elliptical tubes through protruding bumps.

[0041] The above detailed description is a specific description of a feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the patent scope of this case.

Claims

1. A method for recycling imidacloprid wastewater by MVR coupling multi-effect distillation, characterized by: The method includes a light removal tower, a heavy removal tower, a distillation tower, an MVR compressor, an MVR falling film reboiler and an MVR distilled water tank, and the resource recovery method includes the following steps: Step 1: The pesticide wastewater raw liquid from the production workshop is heated and then enters the light components removal tower. After decompression and separation in the tower, the light components dichloroethane and methanol obtained at the top of the tower are pumped to the plant recovery system. The non-condensable gases in the light components removal tower are extracted by a vacuum pump and discharged to the workshop exhaust gas treatment system. Step 2: The liquid after light removal in the de-lightening tower is pumped to the de-weighting tower for heating and flash separation. The water vapor enters the MVR compressor for compression to increase enthalpy and temperature, then enters the MVR falling film reboiler shell side to release the latent heat of condensation and is collected in the MVR distilled water tank; the liquid after flash evaporation in the de-weighting tower and the circulating liquid are pumped together through the falling film circulation pump to the MVR falling film reboiler tube side, absorb the latent heat released by the shell side steam and then flow back to the de-weighting tower; the distilled water collected in the distilled water tank is pumped to the distilled water stock heater to further release some sensible heat, and then returned to the washing workshop for reuse after cooling; Step 3: A portion of the liquid rich in imidazolidine and DMF is extracted from the bottom of the deweighting tower and pumped into the distillation tower for vacuum distillation. The DMF and a small amount of water vapor evaporated after distillation are pumped to the plant recovery system production line for reuse. The remaining imidazolidine-rich mother liquor is cooled to recover the imidazolidine and return it to the production line for reuse.

2. A device for realizing the MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 1, characterized in that: The device includes a raw liquid tank, a secondary raw liquid heater, a raw liquid pump, a light removal condenser, a light removal tank, a light removal reboiler, a light removal circulation pump, a light removal liquid pump and a light removal extraction pump; the raw liquid tank and the secondary raw liquid heater are provided in front of the light removal tower, and the heat sources of the secondary raw liquid heater come from the recovered MVR distilled water and the sensible heat of the condensed water of the light removal tower and the distillation tower respectively; the secondary raw liquid heater includes a distilled water raw liquid heater and a condensed water raw liquid heater connected thereto; the raw liquid tank inlet is connected to the raw material liquid from the production workshop through a connecting pipe, the raw liquid pump inlet is connected to the raw liquid tank, and the raw liquid pump outlet is connected to the distilled water raw liquid heater; the top of the light removal tower is connected to the degassing tower respectively The light condenser is connected to the light removal tank, the bottom of the light removal tower is connected to the bottom pipe side of the light removal reboiler through the light removal circulation pump, and the upper pipe side of the light removal reboiler is connected to the lower part of the light removal tower; the light removal condenser and the light removal tank are also connected to a light removal vacuum pump for extracting non-condensable gases in the light removal tower; the bottom of the light removal tank is connected to the plant recovery system through the light removal extraction pump; the bottom of the light removal tower is connected to the heavy removal tower through the light removal liquid pump; the heat source of the light removal reboiler comes from the plant heating steam, the heating steam goes through the shell side, and after releasing the latent heat, it is connected to the condensate raw liquid heater through the second condensate recovery interface, and is recycled after further releasing the sensible heat in the condensate raw liquid heater.

3. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 2, characterized in that: The device also includes a falling film circulation pump, a deweighting liquid pump, a distilled water reflux pump, a distilled water recovery pump and a first condensed water recovery interface; the top of the deweighting tower is connected to the MVR compressor, and the MVR compressor is connected to the upper shell side of the MVR falling film reboiler; the bottom tube side of the MVR falling film reboiler is connected to the lower part of the deweighting tower, and the top of the MVR falling film reboiler tube side is connected to the bottom of the deweighting tower through the falling film circulation pump; the bottom of the MVR falling film reboiler shell side is connected to the MVR distilled water tank, and the outlet of the MVR distilled water tank is connected to the distilled water stock liquid heater in sequence through the distilled water recovery pump and the first condensed water recovery interface, and the outlet of the MVR distilled water tank is also connected to the upper part of the deweighting tower through the distilled water reflux pump; the bottom of the deweighting tower is connected to the distillation tower through the deweighting liquid pump.

4. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 3, characterized in that: The device also includes a distillation condenser, a concentration separation tank, a distillation reboiler, a DMF concentrate extraction pump, an imidazolidine concentrate extraction pump, a forced circulation pump and a distillation vacuum pump; the top outlet of the distillation tower is connected to the distillation condenser, the concentration separation tank is connected to the upper inlet of the distillation tower, and one outlet of the distillation condenser is connected to the connecting pipeline between the concentration separation tank and the distillation tower through a connecting pipe; the concentration separation tank and the distillation condenser are connected to the distillation vacuum pump in parallel, and are connected to the workshop exhaust gas treatment system through the distillation vacuum pump. The bottom of the concentration separation tank is connected to the plant recovery system through the DMF concentrate extraction pump; the bottom of the distillation tower is connected to the bottom pipe side of the distillation reboiler through the forced circulation pump, the top of the distillation reboiler pipe side is connected to the lower part of the distillation tower, the lower shell side of the distillation reboiler is connected to the condensed water raw liquid heater through the second condensed water recovery interface, the heat source of the distillation reboiler comes from the plant heating steam and enters the distillation reboiler shell side; the bottom of the distillation tower is sent back to the production line for application through the imidazolidine concentrate extraction pump.

5. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 3, characterized in that: The MVR falling film reboiler adopts twisted elliptical tubes as the heater heat exchange tube bundle. A guide tube for wrapping the heat exchange tube bundle is provided in the cylinder of the MVR falling film reboiler.

6. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 4, characterized in that: The light removal reboiler and the rectification reboiler both adopt heat exchange tube bundles with twisted elliptical tubes arranged in parallel; the distilled water stock heater and the condensed water stock heater adopt twisted elliptical tube shell and tube heat exchangers or plate heat exchangers.

7. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 2, characterized in that: The light removal tower and the heavy removal tower both adopt a plate tower structure, and the distillation tower adopts a plate tower structure or a packed tower structure.

8. The device for the MVR-coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 6, characterized in that: The heat exchange tube bundles of the shell and tube heater and the reboiler are composed of several twisted elliptical tubes with high specific surface area, which are bundled and form convex contact between the tube bundles to form a mutually supporting structure, forming an axial multi-channel flow channel without the need for baffles or intermediate supporting tube sheets; the cross-section of the twisted elliptical tubes is nearly elliptical, and is twisted into a spiral structure through secondary processing.

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