A method for resourceful treatment of formamide production wastewater

Abstract

This invention relates to the field of industrial wastewater treatment technology, specifically disclosing a method for the resource-based treatment of formamide production wastewater. The invention first pre-treats the formamide production wastewater using microbubbles followed by freezing, effectively reducing impurity inclusions in the crystallized formamide solid and improving the separation efficiency of formamide from the wastewater. Then, the obtained crude formamide solid is dissolved in water, and the microbubble pre-treatment and freezing steps are repeated until a formamide solid with a purity >95% is obtained. Next, the formamide solid is dissolved in dichloromethane extractant and subjected to microbubble treatment to improve the extraction efficiency of dichloromethane for formamide impurities. After extraction and separation, a formamide product with a purity >99.6% is obtained. The raffinate is distilled to obtain an abamectin byproduct with a content >80%. This invention achieves the resource-based utilization of formamide wastewater, possessing high economic and environmental benefits and significant application value.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for the resource-based treatment of formamide production wastewater. Background Technology

[0002] Formamide is highly reactive and has excellent solubility, making it widely used in organic synthesis, pharmaceuticals, and the fiber industry. It can undergo reactions such as dehydration, decarbonization, grafting acyl groups, and cyclization. It can be used to produce sulfonamide drugs, vitamins, and as a softener for paper and fibers. It has also found wide applications in pesticides, pigments, fragrances, and auxiliaries, and has a very promising market prospect.

[0003] Formamide wastewater originating from avermectin extraction and refining processes mainly contains formamide, avermectin, and other organic matter. The wastewater has a high organic content and is highly toxic, making it unsuitable for direct entry into wastewater biological treatment systems. Currently, the industry generally treats formamide-containing wastewater according to hazardous waste management regulations, resulting in high treatment costs and the inability to recover the formamide, leading to resource waste. Due to formamide's excellent solubility—miscible with water, many alcohols, and organic solvents—and its low boiling point (partially decomposing above 220°C at normal pressure and above 70.5°C at 133.3 Pa pressure), conventional methods for concentrating and recovering formamide, such as heating evaporation concentration, vacuum concentration, organic membrane treatment, and adsorption, are insufficient. To reduce hazardous waste emissions and lower wastewater treatment costs for enterprises, developing a low-cost method for treating formamide wastewater that can recover multiple components is imperative. Summary of the Invention

[0004] To address the problem of the inability to utilize formamide production wastewater for resource recovery, this invention provides a method for treating formamide production wastewater. This method primarily employs microbubble treatment coupled with repeated freeze-crystallization, distilled water washing, and dichloromethane extraction. This not only treats the wastewater but also recovers formamide and avermectin from it. The recovered formamide achieves a purity of over 99%, and the avermectin a purity of over 80%, both of which can be directly sold as products, increasing enterprise profits and demonstrating significant economic and environmental benefits.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A method for the resource-based treatment of formamide production wastewater includes the following steps:

[0007] S1, formamide production wastewater is treated with microbubbles, and then subjected to gradient freezing at -30℃~0℃ to separate solid and liquid, yielding solid formamide a;

[0008] S2, add the solid formamide a to water and mix well to obtain formamide solution a;

[0009] S3, the formamide solution a is subjected to microbubble treatment, and then subjected to gradient freezing at -30℃ to 0℃ to separate solid and liquid, thereby obtaining solid formamide b;

[0010] S4, repeat steps S1-S3 with the formamide solid b until the purity of the obtained formamide solid is >95%, to obtain formamide solid c;

[0011] S5, add the solid formamide c to dichloromethane, subject the resulting formamide solution to microbubble treatment, allow it to stand and separate phases to obtain a liquid formamide product and a dichloromethane extract phase;

[0012] S6, the dichloromethane extract phase is distilled to obtain avermectin and dichloromethane.

[0013] Compared to existing technologies, the resource-based treatment method for formamide production wastewater provided by this invention first pre-treats the wastewater with microbubbles and then freezes it. Microbubbles, with their highly charged particles, large specific surface area, and long residence time in water, alter the thermal stability of the solution. Therefore, microbubble pre-treatment followed by freezing effectively reduces impurity inclusions in the crystallized formamide solid and improves the separation efficiency of formamide from the wastewater. The obtained crude formamide solid is then dissolved in water, and the microbubble pre-treatment and freezing steps are repeated until a formamide solid with a purity >95% is obtained. The formamide solid is then dissolved in dichloromethane extractant and subjected to microbubble treatment to improve the extraction efficiency of dichloromethane for formamide impurities. After extraction and separation, a formamide product with a purity >99.6% is obtained. The raffinate is distilled to obtain an abamectin byproduct with a content >80%, and the dichloromethane obtained from distillation can be reused as an extractant.

[0014] This invention achieves the resource utilization of formamide wastewater through microbubble pretreatment, freezing, extraction, and distillation, with low energy consumption and no secondary pollution. It has high economic and environmental benefits and high application value.

[0015] It should be noted that the formamide production wastewater mentioned in this invention is wastewater generated during the extraction and refining process of abamectin, which mainly contains formamide, abamectin and other organic matter, and water. The content of abamectin is generally about 1%, the content of formamide is about 8%, and the content of other organic matter is about 1%.

[0016] Preferably, in S1 and S3, the microbubble treatment time is 5 min to 10 min.

[0017] Preferably, in S1 and S3, the volume ratio of formamide production wastewater to air flow rate in the microbubble treatment is 100:7 to 100:10, and the proportion of microbubble particles with a diameter of <30μm to all bubbles is >80%.

[0018] Treating formamide production wastewater with microbubbles facilitates more complete crystallization of formamide during subsequent freezing, reduces impurity inclusions in the crystallized formamide solid, and results in higher purity formamide solid obtained by subsequent freeze centrifugation, reducing the number of purification steps and improving separation efficiency.

[0019] Preferably, in S1 and S3, the specific steps of the gradient freezing are as follows: first freezing at -10℃ to 0℃ for 1h to 2h, then freezing at -20℃ to -10℃ for 1h to 2h, and finally freezing at -30℃ to -20℃ for 2h to 3h.

[0020] Preferably, in S1 and S3, the cooling rate of the gradient freezing is 0.2℃ / min to 0.4℃ / min.

[0021] During the research and development process, the inventors discovered that the conventional one-step freezing method for formamide wastewater resulted in formamide solids containing numerous other impurities, leading to high purification difficulty, cost, and energy consumption. Consequently, only formamide products with high impurities could be obtained. Through innovative thinking, the inventors pretreated the formamide production wastewater with microbubbles, followed by gradient freezing, effectively reducing the impurity content in the crystallized formamide solids. This significantly simplified the purification process and reduced energy consumption and costs. Generally, repeating the microbubble pretreatment-gradient freezing process 2-5 times is sufficient to obtain formamide solids with a purity >95%, making the operation simple and efficient.

[0022] In one specific embodiment of the present invention, a refrigerated centrifuge is used to separate the frozen solid-liquid mixture by centrifugation.

[0023] Specifically, the speed of the refrigerated centrifuge is 3000 r / min to 4000 r / min, the centrifugation temperature is -3℃ to 0℃, and the centrifugation time is 3 min to 5 min.

[0024] Preferably, step S2 further includes: exchanging heat between solid formamide a and the formamide production wastewater to be treated through a non-contact heat exchanger to obtain molten formamide; then adding water to the molten formamide and mixing it evenly to obtain formamide solution a; and returning the heat-exchanged formamide production wastewater to step a for wastewater treatment.

[0025] By exchanging heat between the formamide wastewater to be treated (at a temperature of 20-30°C) and the formamide solid obtained by freeze centrifugation, not only can the melting rate of formamide be accelerated, but the formamide production wastewater is also pre-cooled, reducing the energy consumption of subsequent formamide wastewater freezing.

[0026] Preferably, in S2, the mass ratio of formamide solid a to water is 10:1 to 15:1.

[0027] Preferably, in S2, the temperature of the melting formamide is controlled to be 5°C to 10°C.

[0028] It should be noted that in step S4, when repeating steps S1-S3, the amount of water added to obtain solid formamide each time can be adjusted according to the actual process. The specific mass ratio of solid formamide to water is 1:15 to 1:20. The gradient freezing time during each repetition can be adjusted according to the actual freezing conditions.

[0029] Preferably, step S5 further includes: exchanging heat between solid formamide c and the formamide production wastewater to be treated through a non-contact heat exchanger to obtain molten formamide; then adding dichloromethane to the molten formamide and mixing it evenly; and returning the heat-exchanged formamide production wastewater to step a for wastewater treatment.

[0030] By exchanging heat between the formamide production waste liquid and the solid formamide, the formamide can be dissolved. At the same time, the formamide production waste liquid also obtains a lower temperature, achieving the effect of pre-cooling treatment, thereby saving electricity.

[0031] It should be noted that the separated liquids obtained from each centrifugal separation step are combined and then enter the wastewater treatment biological system for further biological treatment. After the treatment meets the standards, the wastewater can be discharged.

[0032] Preferably, in S5, the mass ratio of the molten formamide to dichloromethane is 8:1 to 10:1.

[0033] Using dichloromethane as an extractant can effectively extract avermectin encapsulated in formamide. Furthermore, dichloromethane has a high solubility for avermectin, which can effectively reduce the amount of extractant used, reduce equipment volume and solvent consumption. In addition, dichloromethane has good safety, which can improve the safety of wastewater treatment processes.

[0034] Preferably, in step S5, the microbubble treatment time is 20 min to 30 min.

[0035] Preferably, in S5, the volume ratio of formamide solution to air flow rate in the microbubble treatment is 100:7 to 100:10, and the proportion of microbubble particles with a diameter of <30μm to all bubbles is >80%.

[0036] Dissolving formamide in dichloromethane, followed by microbubble pretreatment and then allowing it to settle and precipitate, can effectively improve the extraction rate and efficiency of dichloromethane for abamectin, resulting in a purity of >95% for the separated formamide.

[0037] Specifically, in S5, the settling time is 2h to 3h.

[0038] Preferably, in S6, the distillation is atmospheric distillation, the bottom temperature of the distillation column is 48℃~115℃, the liquid temperature in the column is 43℃~110℃, the top temperature is 40℃~110℃, and the reflux ratio is 10:1~5:1.

[0039] The formamide production wastewater treatment method provided by this invention, through microbubble treatment coupled with repeated freeze-crystallization, dichloromethane extraction, and distillation, achieves the recovery of formamide and avermectin, solving the problem of the inability to utilize formamide production wastewater as a resource. Furthermore, the treated formamide and avermectin are of high purity and can be directly sold, increasing enterprise profits. This invention not only achieves comprehensive treatment and resource utilization of formamide production wastewater but also reduces environmental treatment costs and improves raw material utilization, demonstrating high economic and environmental benefits and significant potential for widespread application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] To better illustrate the present invention, further examples are provided below.

[0042] The formamide wastewater treated in the following examples and comparative examples contained 1% abamectin, 8.9% formamide, 1.3% other organic matter, and 88.8% water.

[0043] Example 1

[0044] This invention provides a method for treating formamide wastewater, comprising the following steps:

[0045] Step a: 15L of formamide production wastewater was added to a microbubble device for treatment for 5 minutes. The microbubble inlet flow rate was 1L / min, and the formamide wastewater circulation flow rate was 12L / min. Then, it was passed into a refrigeration unit and frozen at -8℃ for 1 hour, then at -15℃ for 2 hours, and finally at -25℃ for 3 hours. The cooling rate was 0.3℃ / min, resulting in a solid-liquid mixture. The solid-liquid mixture was transferred to a refrigerated centrifuge and centrifuged at 3000r / min and -3℃ for 3 minutes to obtain 1.44kg of formamide solid and 13.55kg of liquid. The formamide content was determined to be 85.5%.

[0046] Step b: 1.44 kg of solid formamide and 5 L of formamide production waste liquid at 26 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0047] Step c: Add 140 mL of distilled water to 1.44 g of formamide liquid, then pass it through a microbubble device for 5 min. The microbubble inlet flow rate is 0.1 L / min, and the formamide wastewater circulation flow rate is 1 L / min. Then, pass it through a refrigeration unit and freeze it at -8℃ for 1 h, then at -15℃ for 1 h, and finally at -25℃ for 3 h. The cooling rate is 0.3℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and -3℃ for 3 min to obtain 1.37 kg of formamide solid and 0.20 kg of liquid. The formamide content is determined to be 92.3%.

[0048] Step d: 1.37g of solid formamide and 5L of formamide production waste liquid at 26℃ are subjected to non-contact heat exchange for 1h to obtain a formamide solution at 8℃.

[0049] Step e: Add 70 mL of distilled water to 1.37 g of formamide liquid, then treat it with a microbubble device for 5 min. The microbubble inlet flow rate is 0.05 L / min, and the formamide wastewater circulation flow rate is 0.6 L / min. Then, pass it into a refrigeration unit and freeze it at -8℃ for 1 h, then at -15℃ for 1 h, and finally at -25℃ for 2 h. The cooling rate is 0.3℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and -3℃ for 3 min to obtain 1.33 kg of formamide solid and 0.10 kg of liquid. The formamide content is determined to be 96.1%.

[0050] Step f: 1.33g of solid formamide and 5L of formamide production waste liquid at 26℃ are subjected to non-contact heat exchange for 1h to obtain a formamide solution at 8℃.

[0051] Step g: Add 0.133 kg of dichloromethane to 1.33 g of formamide liquid, then treat it with a microbubble device for 25 min. The microbubble inlet flow rate is 0.05 L / min, the formamide wastewater circulation flow rate is 0.6 L / min, let it stand for 2 h, separate the liquid and obtain 1.28 kg of formamide liquid. The formamide content is determined to be 99.7%.

[0052] In step h, the 0.135 kg dichloromethane extract obtained by separation is distilled under normal pressure. The bottom temperature of the distillation column is 48°C, the liquid temperature in the column is 43°C, the top temperature is 40°C, and the reflux ratio is 10:1, yielding 0.01 kg abamectin (content 81.5%). The dichloromethane obtained by distillation is separated and water is removed for reuse.

[0053] Example 2

[0054] This invention provides a method for treating formamide wastewater, comprising the following steps:

[0055] Step a: 15L of formamide production wastewater was added to a microbubble device for treatment for 8 minutes. The microbubble inlet flow rate was 1L / min, and the formamide wastewater circulation flow rate was 10L / min. Then, it was passed into a refrigeration unit and frozen at 0℃ for 2 hours, then at -10℃ for 2 hours, and finally at -20℃ for 3 hours. The cooling rate was 0.2℃ / min, resulting in a solid-liquid mixture. The solid-liquid mixture was transferred to a refrigerated centrifuge and centrifuged at 3000r / min and 0℃ for 5 minutes to obtain 1.45kg of formamide solid and 13.45kg of liquid. The formamide content was determined to be 86.0%.

[0056] Step b: 1.45 kg of solid formamide and 5 L of formamide production waste liquid at 30 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0057] Step c: Add 130 mL of distilled water to 1.45 kg of formamide liquid, then pass it through a microbubble device for 8 min. The microbubble inlet flow rate is 1 L / min, and the formamide wastewater circulation flow rate is 10 L / min. Then, pass it through a refrigeration unit and freeze it at 0℃ for 1 h, then at -10℃ for 1 h, and finally at -20℃ for 3 h. The cooling rate is 0.2℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and 0℃ for 5 min to obtain 1.36 kg of formamide solid and 0.21 kg of liquid. The formamide content is determined to be 92.5%.

[0058] Step d: 1.36 kg of solid formamide and 5 L of formamide production waste liquid at 30 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0059] Step e: Add 70 mL of distilled water to 1.36 g of formamide liquid, then treat it with a microbubble device for 8 min. The microbubble inlet flow rate is 0.05 L / min, and the formamide wastewater circulation flow rate is 0.7 L / min. Then, pass it into a refrigeration unit and freeze it at 0℃ for 1 h, then at -10℃ for 1 h, and finally at -20℃ for 2 h. The cooling rate is 0.2℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and 0℃ for 5 min to obtain 1.32 kg of formamide solid and 0.1 kg of liquid. The formamide content is determined to be 96.4%.

[0060] Step f: 1.32 kg of solid formamide and 5 L of formamide production waste liquid at 30 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0061] Step g: Add 0.132 kg of dichloromethane to 1.32 kg of formamide liquid, then treat it with a microbubble device for 20 min. The microbubble inlet flow rate is 0.05 L / min, the formamide wastewater circulation flow rate is 0.7 L / min, let it stand for 3 h, separate the liquid, and obtain 1.29 kg of formamide liquid. The formamide content is determined to be 99.7%.

[0062] In step h, the 0.135 kg dichloromethane extract obtained by separation is distilled under normal pressure. The bottom temperature of the distillation column is 48℃~115℃, the liquid temperature in the column is 43℃~110℃, the top temperature is 40℃~110℃, and the reflux ratio is 10:1~5:1, to obtain 0.01 kg abamectin (content 82.1%). The dichloromethane obtained by distillation is separated and reused after removing water.

[0063] Example 3

[0064] This invention provides a method for treating formamide wastewater, comprising the following steps:

[0065] Step a: 15L of formamide production wastewater was added to a microbubble device for treatment for 10 minutes. The microbubble inlet flow rate was 1L / min, and the formamide wastewater circulation flow rate was 14L / min. Then, it was passed into a refrigeration unit and frozen at -10℃ for 1 hour, then at -20℃ for 1 hour, and finally at -30℃ for 2 hours. The cooling rate was 0.4℃ / min, resulting in a solid-liquid mixture. The solid-liquid mixture was transferred to a refrigerated centrifuge and centrifuged at 3000r / min and -2℃ for 4 minutes to obtain 1.43kg of formamide solid and 13.55kg of liquid. The formamide content was determined to be 92.5%.

[0066] Step b: 1.43 kg of solid formamide and 5 L of formamide production waste liquid at 28 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0067] Step c: Add 100 mL of distilled water to 1.43 kg of formamide liquid, then pass it through a microbubble device for 10 min. The microbubble inlet flow rate is 1 L / min, and the formamide wastewater circulation flow rate is 14 L / min. Then, pass it through a refrigeration unit and freeze it at -10℃ for 1 h, then at -20℃ for 1 h, and finally at -30℃ for 2 h. The cooling rate is 0.4℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and -2℃ for 4 min to obtain 1.39 kg of formamide solid and 0.13 kg of liquid. The formamide content is determined to be 91.1%.

[0068] Step d: 1.39 kg of solid formamide and 5 L of formamide production waste liquid at 28 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0069] Step e: Add 70 mL of distilled water to 1.39 kg of formamide liquid, then treat it with a microbubble device for 10 min. The microbubble inlet flow rate is 0.05 L / min, and the formamide wastewater circulation flow rate is 0.6 L / min. Then, pass it into a refrigeration unit and freeze it at -10℃ for 1 h, then at -20℃ for 1 h, and finally at -30℃ for 2 h. The cooling rate is 0.4℃ / min, resulting in a solid-liquid mixture. Transfer the solid-liquid mixture to a refrigerated centrifuge and centrifuge at 3000 r / min and -2℃ for 4 min to obtain 1.35 kg of formamide solid and 0.1 kg of liquid. The formamide content is determined to be 96.0%.

[0070] Step f: 1.35 kg of solid formamide and 5 L of formamide production waste liquid at 28 °C are subjected to non-contact heat exchange for 1 hour to obtain a formamide solution at 8 °C.

[0071] Step g: Add 0.135 kg of dichloromethane to 1.35 kg of formamide liquid, then treat it through a microbubble device for 30 min. The microbubble inlet flow rate is 0.05 L / min, the formamide wastewater circulation flow rate is 0.6 L / min, let it stand for 2 h, separate the liquid, and obtain 1.29 kg of formamide liquid. The formamide content is determined to be 99.6%.

[0072] In step h, the 0.195 kg dichloromethane extract obtained by separation is distilled under normal pressure. The bottom temperature of the distillation column is 48℃~115℃, the liquid temperature in the column is 43℃~110℃, the top temperature is 40℃~110℃, and the reflux ratio is 10:1~5:1, yielding 0.02 kg abamectin (content 76.3%). The dichloromethane obtained by distillation is separated and reused after removing water.

[0073] Comparative Example 1

[0074] This comparative example provides a method for treating formamide wastewater. The method steps and parameters are the same as those in Example 1. The only difference is that the waste liquid in steps a, c, and e is not treated by a microbubble device. All other operations are exactly the same.

[0075] The purity of the final formamide product was 93.7%.

[0076] This indicates that microbubble treatment can reduce the inclusion of crystal impurities and improve the purity of formamide products.

[0077] Comparative Example 2

[0078] This comparative example provides a method for treating formamide wastewater. The method steps and parameters are the same as in Example 1, except that steps a, c, and e do not use gradient freezing. The remaining operations are identical. Specifically, step a involves freezing at -25°C for 6 hours; step c involves freezing at -25°C for 5 hours; and step d involves freezing at -25°C for 4 hours.

[0079] The purity of the final formamide product was 95.2%.

[0080] This indicates that gradient freezing treatment can reduce the inclusion of crystal impurities and improve the purity of formamide products.

[0081] Comparative Example 3

[0082] This comparative example provides a method for treating formamide wastewater. The method steps and parameters are the same as those in Example 1. The only difference is that in step g, the formamide liquid is mixed with dichloromethane but not subjected to microbubble treatment. All other operations are exactly the same.

[0083] The purity of the final formamide product was 97.5%.

[0084] Economic cost estimation

[0085] Taking a veterinary drug manufacturing enterprise in Zhao County, Hebei Province as an example, the amount of formamide wastewater generated is 4m³. 3 The formamide content in the wastewater is approximately 8.9 wt%. Assuming a production period of 300 days per year, the annual formamide wastewater volume can reach 1200 m³. 3 .

[0086] Currently, formamide wastewater is treated as hazardous waste, with a treatment cost of 5500 yuan / ton and an annual treatment fee of 1200 yuan / ton. 3 ×5500 yuan / ton = 660,000 yuan = 6.6 million yuan.

[0087] The estimated cost of treating formamide wastewater according to the formamide wastewater resource recovery method provided by this invention is as follows:

[0088] (1) First microbubbling, freezing and centrifugation treatment 1m 3 The formamide wastewater treatment process requires 100 kWh of electricity and produces 95 kg of formamide mixture and 905 kg of wastewater.

[0089] (2) The second microbubbling, freezing and centrifugation treatment of 95 kg of formamide mixture requires 25 kw·h of electricity, and produces 85 kg of formamide mixture and 19.5 kg of wastewater;

[0090] (3) The third microbubble, freezing and centrifugation treatment of 85 kg of formamide mixture requires 20 kw·h of electricity, and produces 78 kg of formamide mixture and 11.3 kg of wastewater;

[0091] (4) The power consumption required for dichloromethane microbubble treatment of 78kg formamide mixture is 30kw·h (including the energy consumption of distilling dichloromethane), producing 70kg formamide and 5kg abamectin;

[0092] (5) The final formamide content is approximately 99.6%. 70 kg of formamide is recovered. At this concentration, the selling price of formamide is 3500 yuan / ton. Therefore, the revenue from recovering formamide is 0.07 * 3500 = 245 yuan / m³. 3 Wastewater;

[0093] (6) The final abamectin content is about 80%. 5 kg of abamectin is recovered. At this concentration, the selling price of abamectin is 25,000 yuan / ton. Therefore, recovering abamectin can generate a revenue of 5 * 25 = 125 yuan / m³. 3 Wastewater;

[0094] (6) The total amount of wastewater generated is 940 kg. The process required to treat this wastewater is advanced oxidation pretreatment + anaerobic + aerobic + deep treatment. The estimated wastewater treatment cost is 80 yuan / m³. 3 The estimated wastewater treatment cost is approximately 80 * 0.94 = 75.2 yuan / m³. 3 ;

[0095] (7) The total power consumption for freezing crystallization and centrifugal separation is 100 + 25 + 20 + 30 = 175 kWh. Assuming an electricity price of 1 yuan / kWh, the estimated electricity cost for wastewater treatment is 175 yuan / m³. 3 ;

[0096] The total annual treatment cost is (75.2 + 175) * 1200 = 210,000 yuan. The implementation of the new process can generate revenue for the enterprise of (245 + 125) * 1200 = 444,000 yuan. In summary, the application of the formamide wastewater treatment technology provided by this invention not only saves the enterprise 6.6 million yuan, but also generates revenue of 444,000 - 210,000 = 234,000 yuan. Therefore, the treatment method provided by this invention is of great significance for the recovery of formamide from wastewater.

[0097] In summary, the formamide wastewater treatment method provided by this invention can obtain high-purity formamide solution and abamectin byproduct, enabling the resource utilization of formamide wastewater. This is of great significance for reducing environmental protection treatment costs and production costs for enterprises.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the resource-based treatment of formamide production wastewater, characterized in that, Includes the following steps: S1, formamide production wastewater is treated with microbubbles, and then subjected to gradient freezing at -30℃~0℃ to separate solid and liquid, yielding solid formamide a; S2, add the solid formamide a to water and mix well to obtain formamide solution a; S3, the formamide solution a is subjected to microbubble treatment, and then subjected to gradient freezing at -30℃ to 0℃ to separate solid and liquid, thereby obtaining solid formamide b; S4, repeat steps S1-S3 with the formamide solid b until the purity of the obtained formamide solid is >95%, to obtain formamide solid c; S5, formamide solid c is heat-exchanged with the formamide production wastewater to be treated through a non-contact heat exchanger to obtain molten formamide. Then, dichloromethane is added to the molten formamide, and the resulting formamide solution is subjected to microbubble treatment and allowed to stand for phase separation to obtain formamide liquid product and dichloromethane extract phase. S6, the dichloromethane extract phase is distilled to obtain abamectin and dichloromethane; In S1 and S3, the specific steps of the gradient freezing are as follows: first, freeze at -10℃ to 0℃ for 1h to 2h, then freeze at -20℃ to -10℃ for 1h to 2h, and finally freeze at -30℃ to -20℃ for 2h to 3h. The formamide production wastewater is wastewater generated during the avermectin extraction and refining process, and includes formamide, avermectin, other organic matter, and water.

2. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, In S1 and S3, the microbubble treatment time is 5 min to 10 min; and / or In S1 and S3, during the microbubble treatment, the volume ratio of formamide production wastewater to air flow rate is 100:7 to 100:10, and the proportion of microbubble particles with a diameter of <30μm to all bubbles is >80%.

3. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, In S1 and S3, the cooling rate of the gradient freezing is 0.2℃ / min to 0.4℃ / min.

4. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, S2 further includes: exchanging heat between solid formamide a and the formamide production wastewater to be treated through a non-contact heat exchanger to obtain molten formamide; then adding water to the molten formamide and mixing it evenly to obtain formamide solution a; and returning the heat-exchanged formamide production wastewater to step a for wastewater treatment.

5. The method for resource-based treatment of formamide production wastewater as described in claim 4, characterized in that, In S2, the mass ratio of formamide solid a to water is 10:1 to 15:1; and / or In S2, the temperature of the melting formamide is controlled to be 5℃~10℃.

6. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, In step S5, the formamide production wastewater after heat exchange is returned to step a for wastewater treatment.

7. The method for resource-based treatment of formamide production wastewater as described in claim 1 or 6, characterized in that, In S5, the mass ratio of the molten formamide to dichloromethane is 8:1 to 10:

1.

8. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, In S5, the microbubble treatment time is 20 min to 30 min; and / or In S5, during the microbubble treatment, the volume ratio of formamide solution to air flow rate is 100:7 to 100:10, and the proportion of microbubble particles with a diameter of <30μm to all bubbles is >80%.

9. The method for resource-based treatment of formamide production wastewater as described in claim 1, characterized in that, In S6, the distillation is atmospheric distillation, the bottom temperature of the distillation column is 48℃~115℃, the liquid temperature in the column is 43℃~110℃, the top temperature is 40℃~110℃, and the reflux ratio is 10:1~5:1.