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

Abstract

The invention discloses an MVR (mechanical vapor recompression) coupled multi-effect rectification imidacloprid wastewater resource recycling method and device, the device comprises a light component removal tower, a heavy component removal tower, a rectification tower, an MVR compressor, an MVR falling film reboiler and an MVR distilled water tank, pesticide wastewater raw material liquid from a production workshop enters the light component removal tower after being heated, and after being subjected to reduced pressure separation in the light component removal tower, the pesticide wastewater raw material liquid enters the rectification tower; pumping light component substances dichloroethane and methanol obtained at the top of the light component removal tower to a factory recovery system; pumping the feed liquid subjected to light component removal by the light component removal tower to a heavy component removal tower for heating and flash separation; the heavy component removal tower extracts water vapor, the water vapor is used as a heat source to return to the heavy component removal tower reboiler after compression, enthalpy increase and temperature rise to heat the circulating feed liquid, the heavy component feed liquid after distillation and concentration is pumped into the rectifying tower for reduced pressure distillation, and DMF and a small part of water vapor are pumped to a factory recovery system production line for use after rectification. And cooling and recovering the remaining imidazolidine-enriched mother liquor. According to the device, the heat exchange end difference can be reduced, the energy consumption is reduced, and multi-effect rectification pesticide production wastewater resource recovery is realized.

Description

Technical Field

[0001] The 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 pesticide producer in the world. The pollution of the pesticide industry mainly comes from the wastewater discharged during the production process. In 2020, the national pesticide industry discharged about 250 million tons of wastewater each year, mainly involving drainage in the production process, product washing water, equipment and workshop floor cleaning water, etc. Pesticide production wastewater has always been the focus of social attention due to its high toxicity, high concentration and difficulty in treatment. Pesticide production wastewater treatment technology can be divided into physicochemical method, chemical method, biochemical method and incineration method according to different principles. Extraction and distillation are the most widely used physicochemical methods for treating pesticide production wastewater. Since extraction requires the use of solvents, combining distillation to recover solvents is an effective way to avoid secondary pollution of solvents, and it is also convenient to realize the resource reuse of pesticide production wastewater. However, the distillation method consumes a lot of energy and has high treatment costs. The existing multi-effect distillation equipment has a complex structure, a long process flow, 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 to provide a method and device for recycling imidacloprid wastewater by MVR coupling multi-effect distillation.

[0004] The present invention is realized by the following technical scheme: a MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method, 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 material 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 plant recovery system; the non-condensable gas in the light component removal tower is extracted and discharged to the workshop waste gas treatment system through 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. After the water vapor enters the MVR compressor for compression and heat increase, it enters the MVR falling film reboiler shell side to release the condensation latent heat and then is collected in the MVR distilled water tank; the liquid after flash evaporation in the de-weighting tower and the circulating liquid are pumped to the MVR falling film reboiler tube side through the falling film circulation pump, and then refluxed to the de-weighting tower after absorbing the latent heat released by the shell side steam; the distilled water collected in the distilled water tank is pumped to the distilled water stock heater to further release part of the sensible heat, and then returned to the washing workshop for reuse after cooling;

[0007] Step 3: The deweighting tower extracts the feed liquid containing imidazolidine and DMF, which is 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 mother liquor rich in imidazolidine is cooled to recover the imidazolidine and return it to the production line for application.

[0008] A device for realizing a method for recycling imidacloprid wastewater by MVR coupling multi-effect distillation, the device comprises a stock liquid tank, a secondary stock liquid heater, a stock 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 stock liquid tank and the secondary stock liquid heater are arranged in front of the light removal tower, and the heat sources of the secondary stock 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 stock liquid heater comprises a distilled water stock liquid heater and a condensed water stock liquid heater connected thereto; the stock liquid tank inlet is connected to the raw material liquid from the production workshop through a connecting pipe, the stock liquid pump inlet is connected to the stock liquid tank, and the stock liquid pump outlet is connected to the distilled water stock liquid heater; the top of the light removal tower is connected to the light removal condenser The condenser and the de-lightness tank are connected respectively, the bottom of the de-lightness tower is connected to the bottom pipe side of the de-lightness reboiler through the de-lightness circulation pump, and the upper pipe side of the de-lightness reboiler is connected to the lower part of the de-lightness tower; the de-lightness condenser and the de-lightness tank are also connected with a de-lightness vacuum pump for extracting non-condensable gas in the de-lightness tower; the bottom of the de-lightness tank is connected to the plant recovery system through the de-lightness extraction pump; the bottom of the de-lightness tower is connected to the de-heavy tower through the de-lightness liquid pump; the heat source of the de-lightness reboiler comes from the plant heating steam, the de-lightness reboiler is connected to the condensate stock 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 stock liquid heater through the second condensate recovery interface, and is recycled after further releasing the sensible heat in the condensate stock liquid heater. The light components evaporated from the top of the light-removal tower are condensed in the light-removal condenser, with one part refluxed to the light-removal tower and the other part entering 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 in 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 condensate collection system in the plant area; 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 through the distilled water recovery pump and the first condensed water recovery interface in sequence, 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 rising in temperature, 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 stock liquid heater, and after further releasing sensible heat, it returns to the production water washing station for circulation; 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 an 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 waste gas treatment system through the distillation vacuum pump. The bottom of the concentration and 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, the lower shell side of the distillation reboiler is connected to the condensate stock 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 application through the imidazolidine concentrate extraction pump. A part of the DMF-rich condensate condensed from the distillation condenser at the top of the distillation tower is refluxed to the distillation tower, and the other part enters the concentration separation tank for recycling and reuse; there is a distillation reboiler 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, and returns to the condensate collection system of the plant area 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 use.

[0011] The MVR falling film reboiler adopts twisted elliptical tubes as the heater heat exchange tube bundle, and a guide tube for wrapping the heat exchange tube bundle is arranged 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 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 mutual support structure, forming an axial multi-channel flow channel, without the need for baffles or intermediate support tube sheets; the cross section of the twisted elliptical tube is nearly elliptical, and after secondary processing, it is twisted to form a spiral structure. The three-dimensional variable space turbulent flow design with axial multi-channels between the heat exchange tube bundles can reduce the heat exchange end difference, reduce energy loss, and improve heat exchange efficiency.

[0015] Compared with the prior art, the advantages of the present invention are: the device utilizes the latent heat of the steam produced by the de-weighting tower as the heat source of 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 heating at the bottom of the tower, which can greatly reduce the energy consumption of the de-weighting tower and avoid the use of the top condenser to cool and recover the distilled water, thereby reducing the energy consumption and water consumption of the cooling system, and realizing energy saving and water saving in the process of recycling the wastewater from the production of pesticides. 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 transfer 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 realize the low-carbon operation of the multi-effect distillation pesticide production wastewater resource recovery system. The operation 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 It is a structural schematic diagram of an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of a local structure when the heat exchange tube bundle of an embodiment of the present invention adopts twisted elliptical tubes;

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

[0019] Meanings of the reference numerals in the figure: 1. stock liquid tank; 2. distilled water stock liquid heater; 3. condensed water stock liquid heater; 4. de-light tower; 5. de-light condenser; 6. de-light tank; 7. de-light reboiler; 8. de-heavy 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. stock liquid pump; 162. de-light circulation pump; 163. de-light feed liquid pump; 164. de-light 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, delightening 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 content of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] Example

[0022] See also 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 material liquid from the production workshop enters the light component removal tower 4 after being heated. 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 plant recovery system D; the non-condensable gas B in the light component removal tower 4 is extracted and discharged to the workshop waste gas treatment system through 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. After the water vapor enters the MVR compressor 9 for compression and enthalpy increase and temperature rise, it enters the MVR falling film reboiler 10 shell side to release the condensation latent heat 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 to the MVR falling film reboiler 10 tube side through the falling film circulation pump 165, and then refluxed to the de-weighting tower after absorbing the latent heat released by the shell side steam; 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 feed 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] In this recovery method, the purpose is to utilize the imidazolidine dissolved in the dichloroethane solution of imidacloprid to dissolve the imidazolidine in hot water through different solubility. The hot water after dissolving the imidazolidine contains impurities such as DMF, dichloroethane and methanol, and a multi-stage distillation process is used to recover DMF and imidazolidine. The light components such as dichloroethane and methanol are removed at the top of the light removal tower 4; the hot water containing DMF and imidazolidine is extracted from the bottom of the light removal tower 4 and then goes to the heavy removal tower 8. The heavy removal tower 8 adopts the MVR distillation method, and the steam extracted from the top of the tower is compressed by the MVR compressor 9 to increase the enthalpy and then returns to the MVR falling film reboiler 10 at the bottom of the tower to provide heat for the reboiling at the bottom of the tower to release the latent heat. The distilled water enters the raw liquid heater to further release the latent heat and then returns to the production water washing station F for recycling; the mother liquor containing imidazolidine and DMF is extracted from the bottom of the heavy removal tower 8, and DMF is evaporated after distillation and applied to the production line, and the remaining mother liquor is cooled to recover the imidazolidine and return to the production line for application.

[0027] A device for realizing a method for recycling imidacloprid wastewater by MVR coupling multi-effect distillation, the device comprises a stock liquid tank 1, a secondary stock liquid heater, a stock 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 stock liquid tank 1 and a secondary stock liquid heater are arranged in front of a light removal tower 4, and the heat sources of the secondary stock 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 stock liquid heater comprises a distilled water stock liquid heater 2 and a condensed water stock liquid heater 3 connected thereto; the inlet of the stock liquid tank 1 is connected to the raw material liquid A from the production workshop through a connecting pipe, the inlet of the stock liquid pump 161 is connected to the stock liquid tank 1, and the outlet of the stock liquid pump 161 is connected to the distilled water stock 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-lightness tank 6 are connected separately, the bottom of the de-lightness tower 4 is connected to the bottom pipe side of the de-lightness reboiler 7 through the de-lightness circulation pump 162, and the upper pipe side of the de-lightness reboiler 7 is connected to the lower part of the de-lightness tower 4; the de-lightness condenser 5 and the de-lightness tank 6 are also connected to a de-lightness vacuum pump 171 for extracting the non-condensable gas B in the de-lightness tower 4; the bottom of the de-lightness tank 6 is connected to the plant recovery system D through the de-lightness extraction pump 164; the bottom of the de-lightness tower 4 is connected to the de-heavy tower 8 through the de-lightness liquid pump 163; the heat source of the de-lightness reboiler 7 comes from the plant heating steam C, and the de-lightness reboiler 7 is connected to the condensate stock 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 stock liquid heater 3 through the second condensate recovery interface 182, and is further released in the condensate stock liquid heater 3. Recyclable. The light components evaporated from the top of the light removal tower 4 are condensed in the light removal condenser 5, part of which flows back to the light removal tower 4, and the other part enters the light removal tank 6 for recovery; there is a light removal reboiler 7 at the bottom of the light removal tower 4, and the heat source comes from the heating steam C in the plant area. The heating steam goes through the shell side, and after releasing the latent heat, it is sent to the condensate stock heater 3 through the second condensate recovery interface 182, and returns to the condensate collection system G in the plant area after further releasing the sensible heat; 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 light removal vacuum pump 171 is set to ensure the vacuum operation of the system while extracting the non-condensable gas in 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 tube side of the MVR falling film reboiler 10 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 liquid heater 2 through the distilled water recovery pump 168 and the first condensed water recovery interface 181 in sequence, 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, and then enters the MVR distilled water tank 11 after releasing latent heat; 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 the material is refluxed to the de-weighting tower 8 after falling film heating in the heater tube; the MVR distilled water tank 11 collects the condensed water of 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 stock liquid heater 2, and after further releasing sensible heat, it is returned to the production water washing station F for circulation; 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 an 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 steam evaporated from the rectifying condenser 13 at the top of the rectifying tower 12 flows 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 the heat source comes from the heating steam in the plant area, and the second condensed water recovery interface 182 is sent to the condensed water stock heater 3, and returns to the condensed water collection system G in the plant area after releasing the sensible heat; a discharge pump (imidazolidine concentrate extraction pump 169) is provided at the bottom of the rectifying tower 12 to extract the concentrate rich in imidazolidine and pump it back to the production line for application. In this embodiment, the setting of the distillation vacuum pump 172 ensures the vacuum operation of the system while extracting the non-condensable gas of 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 then is 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 light removal tower 4. After the heated raw material liquid A enters the light removal tower 4, it enters the light removal reboiler 7 under the action of the light removal circulation pump 162 together with the feed liquid in the light removal tower 4, and returns to the light removal tower 4 after being heated. At this time, the high-temperature feed liquid enters the light removal tower 4 and is separated by reduced pressure. The light components such as dichloroethane and methanol evaporate, and at the same time contain part of the water vapor, and enter the light removal condenser 5 and the light removal tank 6 at the top of the tower for separation. At the same time, part of the condensate refluxes to the top of the light removal tower 4; the non-condensable gas of the light removal system is extracted and discharged to the workshop waste gas treatment system by the light removal vacuum pump 171, and the light removal extraction pump 164 of the light removal tower 4 is connected to the bottom of the light removal tank 6, and the extracted light components are pumped to the plant area 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 stripping section, and is pumped to the top of the MVR falling film reboiler 10 by the falling film circulation pump 165, and returns to the lower part of the de-weighting tower 8 after being heated by the falling film on the tube side; 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, condenses after releasing the latent heat, and after the distilled water enters the MVR distilled water tank 11, a part of it is pumped to the distilled water stock liquid heater 2 by the distilled water recovery pump 168, further releases part of the sensible heat, and then returns to the 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-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, and part of the condensate flows back 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, and the extracted DMF concentrate is pumped to the plant recovery system D; an imidazolidine concentrate extraction pump 169 is provided at the bottom of the distillation tower 12 to pump the liquid after the DMF is removed to the washing workshop for reuse.

[0033] The present embodiment provides a method for resource recovery of wastewater from the washing process of imidacloprid production by MVR-coupled multi-effect distillation, with the aim of developing a method technology for resource recovery of pesticide production wastewater by multi-effect distillation coupled with an MVR heat pump, and combining the design method of a three-dimensional turbulent flow heat exchange device to maximize the use of waste heat from the multi-effect distillation process, thereby improving the energy utilization level of resource recovery of pesticide production wastewater by multi-effect distillation, and thus greatly reducing the energy cost of wastewater resource recovery; the design method of a three-dimensional turbulent flow heat exchange device 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 the 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 operating reliability of the heat exchange device can be improved.

[0034] The MVR coupled multi-effect distillation method for recycling wastewater from the washing process of imidacloprid production in this embodiment is compared with the distillation system represented by multi-effect distillation or single-effect MVR heat pump distillation. Due to the use of heat exchange equipment with three-dimensional turbulent design and optimization method, the heat exchange temperature and pressure of the MVR heat exchange equipment can be reduced, the MVR compression power consumption can be reduced, and the waste heat resources of the distillation system can be used to the maximum extent, which greatly improves the energy level of wastewater recycling. Taking this implementation case as an example, after adopting the MVR coupled multi-effect distillation wastewater recycling process for the washing process of imidacloprid production, the unit imidazoline recycling energy consumption is reduced by more than 75% compared with the traditional single-effect distillation system; compared with the traditional three-effect distillation wastewater recycling process for the washing process of imidacloprid production, the unit imidazoline recycling energy consumption is reduced by 30% to 50%; in addition, due to the use of MVR technology, no 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 recycling in the washing process of imidacloprid production, and realize low-carbon recycling 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 arranged 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 stock heater 2 and the condensed water stock 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 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 mutual support structure, forming an axial multi-channel flow channel, without the need for baffles or intermediate support tube sheets; the cross-section of the twisted elliptical tube is nearly elliptical, and is twisted to form a spiral structure after secondary processing. The three-dimensional variable space turbulent flow design with axial multi-channels between the heat exchange tube bundles can reduce the heat exchange end difference, reduce energy loss, and improve heat exchange efficiency. The heat exchange tube bundle adopts twisted elliptical tubes with high specific surface area. The twisted elliptical tubes are mutually supported by convex contact to form a stable structure, which has good heat exchange effect and is conducive to heat recovery. The three-dimensional variable space turbulent flow design with axial multi-channels between the heat exchange tube bundles and the twisted elliptical tubes with a nearly elliptical cross-section design make the flow in the three-dimensional variable space without dead angles, eddy current points, wear angles, and 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 convex points.

[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 deviate 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 in that: 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: Step 1: The pesticide wastewater raw material 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 plant recovery system; the non-condensable gas in the light component removal tower is extracted and discharged to the workshop waste gas treatment system through a vacuum pump; Step 2: The liquid after light removal in the de-lightening tower is pumped to the de-weighting tower for heating and flash separation. After the water vapor enters the MVR compressor for compression and heat increase, it enters the MVR falling film reboiler shell side to release the condensation latent heat and then is collected in the MVR distilled water tank; the liquid after flash evaporation in the de-weighting tower and the circulating liquid are pumped to the MVR falling film reboiler tube side through the falling film circulation pump, and then refluxed to the de-weighting tower after absorbing the latent heat released by the shell side steam; the distilled water collected in the distilled water tank is pumped to the distilled water stock heater to further release part of the 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 after distillation, it is pumped to the distillation tower for vacuum distillation. After distillation, DMF and a small amount of water vapor are evaporated and pumped to the production line of the plant recovery system for application. The remaining mother liquor rich in imidazolidine is cooled to recover the imidazolidine and return it to the production line for application.

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 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 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 light removal condenser The condenser and the de-lightness tank are connected respectively, the bottom of the de-lightness tower is connected to the bottom pipe side of the de-lightness reboiler through the de-lightness circulation pump, and the upper pipe side of the de-lightness reboiler is connected to the lower part of the de-lightness tower; the de-lightness condenser and the de-lightness tank are also connected with a de-lightness vacuum pump for extracting non-condensable gas in the de-lightness tower; the bottom of the de-lightness tank is connected to the plant recovery system through the de-lightness extraction pump; the bottom of the de-lightness tower is connected to the de-heavy tower through the de-lightness liquid pump; the heat source of the de-lightness 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 stock liquid heater through the second condensate recovery interface, and is recycled after further releasing the sensible heat in the condensate stock heater.

3. The device of the MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 2 is 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 through the distilled water recovery pump and the first condensed water recovery interface in sequence, 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 of the MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 3 is 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 an 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 waste gas treatment system through the distillation vacuum pump. system; 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 condensate stock 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 application through the imidazolidine concentrate extraction pump.

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

6. The device of the MVR coupled multi-effect distillation imidacloprid wastewater resource recovery method according to claim 4 is 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 bundle of the shell and tube heater and the reboiler is composed of a number of twisted elliptical tubes with high specific surface area, which are bundled and formed into a mutually supporting structure so as to form convex contact between the tube bundles, thereby forming an axial multi-channel flow channel without the need for baffles or intermediate supporting tube sheets; the cross-section of the twisted elliptical tube is nearly elliptical, and is twisted to form a spiral structure after secondary processing.

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