Preparation method of abamectin wet powder

Abstract

The invention discloses a preparation method of abamectin wet powder, which comprises the following steps: dissolving an abamectin crude product by using methanol, carrying out concentration control, cooling and crystallizing, continuously dissolving and concentrating a secondary refined product by using methanol for further purification, slowly cooling at a low rotating speed to complete crystallization, carrying out filter pressing, and drying to obtain the abamectin wet powder. Continuously dissolving and concentrating a secondary refined product obtained after filter pressing by using methanol, purifying again, slowly cooling at a low rotating speed to complete crystallization, then carrying out filter pressing, continuously dissolving a secondary refined product obtained after filter pressing by using methanol, adding carbon, filtering and decolorizing, and slowly cooling at a low rotating speed to complete crystallization; and carrying out mother liquor filter pressing, stirring and washing and negative-pressure constant-temperature drying on the obtained filtered crystallization liquid to obtain an abamectin wet high-quality product with flowability. The production process provided by the invention effectively solves the problems of strong adhesiveness, small crystal and poor crystal form of the wet high-quality abamectin material, ensures that the flow velocity is stable, wall adhesion and caking are avoided when the wet high-quality abamectin material is used in subsequent automatic feeding and discharging equipment, and can effectively improve the production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of biological pesticides, and in particular to a method for preparing avermectin wet powder. Background Art

[0002] As a broad-spectrum beta-lactamase inhibitor, avermectin can be used in combination with beta-lactam antibiotics to enhance their antibacterial activity. With the continuous increase of antibiotic resistance, avermectin has attracted much attention as a new antibiotic adjuvant. With the improvement of people's living standards and the call for green food, biological pesticides are very popular in the current pesticide market. Authoritative sources predict that the 21st century will be the century of biological pesticides, and European biological pesticides will increase from US$100 million in sales in 1997 to US$169 million in 2004. According to the "2022-2027 China Abamectin Industry Operation Status and Investment Prospects Survey Research Report", the market size of avermectin will reach about US$750 million worldwide in 2022, of which China is one of the largest consumer countries. Specifically, the global annual consumption of avermectin reaches more than 100,000 tons. In recent years, with the support of policies and the increasing demand in the medical and agricultural fields, the avermectin market has brought new development opportunities. In the domestic avermectin market, there are more than 10 technical manufacturers in my country, and nearly 300 companies have obtained formal registration for pesticides. The avermectin pesticides currently on the market include avermectin ointment, avermectin technical powder, ivermectin powder and avermectin benzoate powder.

[0003] In the previous avermectin production process, the wet fine powder after multiple recrystallization and drying has strong adhesion and poor fluidity. The process method is: add 550kg of avermectin sub-fine powder to the double cone, maintain negative pressure cold extraction for 1h, keep warm at 50℃ for 3h, and then cool down for unloading. The wet fine powder in the unloading process after drying has a slow flow rate when the powder is poured, has strong adhesion, small crystals, and poor crystal shape. The existing process technology and equipment are outdated and cannot meet the needs of current enterprise development. It is not conducive to the transportation or use of customers in subsequent use, and the market product competitive advantage is weakened. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing avermectin wet powder, which improves the fluidity of the product through a three-in-one process (filter pressing, elution and drying in one), combined with a verified and optimized recrystallization and drying process mode. The process has low rotation speed and slow cooling. After the crystallization and crystal growing processes are completed, elution is implemented, a reasonable temperature is controlled, and negative pressure drying is adopted in combination with the characteristics of the three-in-one process, so as to produce avermectin wet fine products with large crystals and good fluidity, and the labor intensity of repeated feeding and unloading when using a double cone is reduced, and the environmental health and safety risks are also reduced, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing avermectin wet powder comprises the following steps:

[0007] S1: Use methanol to dissolve the crude avermectin, keep it warm and dissolve it, then distill it at normal pressure, then cool it down and crystallize it after concentration control, then filter it at room temperature, and obtain fine products one by one after another after filter pressing;

[0008] S2: Add methanol to dissolve the first-pass fine product, repeat step S1, and filter to obtain the second-pass fine product;

[0009] S3: The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step S2 is repeated to obtain a third-pass crystallization liquid, which is pressed into a filter drying device;

[0010] S4: The obtained crystal liquid after filtration is subjected to solid-liquid filtration separation in a filter drying device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is filtered again to remove potential sugars and impurities carried by the material.

[0011] S5: The semi-finished product after the filter press is filtered by the mother fluid, rinsed and stirred, and heated and dried in the filter drying equipment, and the negative pressure is maintained for drying. Then the steam valve is adjusted, and the crystal is slowly heated up and then kept warm. After that, the temperature is lowered and the material is unloaded to obtain the avermectin wet powder with large crystals and fluidity.

[0012] Furthermore, after dissolution in S1, the rotation speed of the crystallization tank is adjusted to 30HZ.

[0013] Furthermore, after the cooling and crystallization in S1, the rotation speed is adjusted to 15HZ-30HZ.

[0014] Furthermore, the cooling time in S1 is controlled to be 3h.

[0015] Furthermore, in S3, charcoal is added for filtration and decolorization, the cooling time is controlled to be 3h, the cooling speed is controlled to be 15HZ, and three crystallization solutions are obtained.

[0016] Furthermore, the regulating steam valve is slowly heated to 75°C-85°C at a rate of 6-8°C / 10min for heat preservation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The three-in-one (filter pressing, elution washing and drying in one) production process of the present invention effectively solves the problems of strong adhesion, small crystals and poor crystal shape of wet fine avermectin materials, ensuring that the flow rate is stable, does not stick to the wall and does not agglomerate when the subsequent automatic feeding and unloading equipment is used, and can effectively improve production efficiency;

[0019] 2. We can obtain a fluid avermectin wet fine product because the slow rotation speed of avermectin during cooling will cause the precipitated crystals to continue to absorb crystals and gradually become larger. The crystal shape is relatively good. When the material is piled up, the gaps between the crystals are large, which makes the material itself fluid and enhances the competitive advantage of the market product.

[0020] 3. It can be completed in one step during the production process, reducing labor intensity and safety risks, improving environmental hygiene and health, saving production time and costs, and is indeed a safe and efficient method. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1: A three-in-one (filter pressing, elution washing, drying in one) method for preparing avermectin wet powder, recrystallization method - cooling crystallization speed demonstration:

[0023] (1) Using methanol to dissolve the crude avermectin, the speed of the crystallizer is adjusted to 30 Hz, and after heat preservation and dissolution, atmospheric distillation is performed. After concentration control, the temperature is lowered and the crystallization speed is 30 Hz. The cooling time is controlled to be 3 hours and the temperature is lowered to room temperature for pressure filtration. After pressure filtration, fine products are obtained one by one;

[0024] (2) adding methanol to the fine product of the first pass to dissolve it, repeating step (1) and filtering to obtain the fine product of the second pass;

[0025] (3) The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step (2) is repeated to obtain a third-pass crystallization liquid, which is then pressed into the three-in-one;

[0026] (4) The filtered crystal liquid obtained above is subjected to solid-liquid pressure filtration separation in a three-in-one device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is then filtered again to remove potential sugars and impurities carried by the material.

[0027] (5) The semi-finished product after the above-mentioned pressure filtration is subjected to mother fluid filtration, elution and stirring, heating and drying in a three-in-one process, and maintained under negative pressure drying. Then, the steam valve is adjusted to slowly heat the crystal to 75°C at a rate of 6°C / 10min for insulation, and then the temperature is lowered and the material is unloaded.

[0028] The obtained avermectin wet fine product has slight fluidity, but the crystals are small and the crystal shape is relatively poor. The sample was sent for testing, and the repose angle was 52.

[0029] Using the process of this embodiment, the experiments of Examples 2-5 were also carried out. This time, 5 batches of experiments (Examples 1-5) were arranged to carry out case demonstration. Since the processes of the 5 batches of experiments are exactly the same, the specific processes of Examples 1-5 will not be described in detail here.

[0030] Conclusion description: Although the subsequent drying equipment was replaced from a double cone to a three-in-one (filter pressure, elution, and drying in one), and one elution was added, the stirring speed of the crystallization tank was too fast during the cooling process, which would destroy the crystal formation process of the material during the crystal growth and crystallization during the cooling process, resulting in small crystals and poor crystal shape. At the same time, the fluidity would also be affected to a certain extent. The final repose angle was 52. The final repose angle index embodiments 1-5 were 52, 54, 50, 55, and 54, respectively. See Table 1 for details.

[0031] Table 1 Repose angle index of Examples 1-5

[0032] Stirring frequency Cooling time Drying equipment Controlling temperature Angle of repose Example 1 30HZ 3h triple 75℃ 52° Example 2 30HZ 3h triple 75℃ 54° Example 3 30HZ 3h triple 75℃ 50° Example 4 30HZ 3h triple 75℃ 55° Example 5 30HZ 3h triple 75℃ 54°

[0033] Example 6: A three-in-one (filter pressing, elution washing, drying in one) method for preparing avermectin wet powder, recrystallization method - cooling crystallization time demonstration:

[0034] (1) Using methanol to dissolve the crude avermectin, the rotation speed of the crystallizer is adjusted to 30 Hz, and after heat preservation and dissolution, atmospheric distillation is performed. After concentration control, the temperature is lowered and the crystallization speed is 15 Hz. The cooling time is controlled to 1 hour and the temperature is lowered to room temperature for pressure filtration. After pressure filtration, fine products are obtained one by one;

[0035] (2) adding methanol to the fine product of the first pass to dissolve it, repeating step (1) and filtering to obtain the fine product of the second pass;

[0036] (3) The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step (2) is repeated to obtain a third-pass crystallization liquid, which is then pressed into the three-in-one;

[0037] (4) The filtered crystal liquid obtained above is subjected to solid-liquid pressure filtration separation in a three-in-one device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is then filtered again to remove potential sugars and impurities carried by the material.

[0038] (5) The semi-finished product after the above-mentioned pressure filtration is subjected to mother fluid filtration, elution and stirring, heating and drying in a three-in-one process, and maintained under negative pressure drying. Then, the steam valve is adjusted to slowly heat the crystal to 75°C at a rate of 6-8°C / 10min for insulation, and then the temperature is lowered and the material is unloaded.

[0039] The obtained wet fine product of avermectin has slight fluidity but tiny crystals, and the angle of repose of the sample tested is 55.

[0040] Using the process of this embodiment, the experiments of Examples 6-10 were also carried out. Five batches of experiments were arranged to carry out example demonstration. Since the processes of the five batches of experiments are exactly the same, the specific processes of Examples 6-10 will not be described in detail here.

[0041] Conclusion: Although the subsequent drying equipment was changed from double cone to three-in-one and one elution was added, the short cooling time after distillation would affect the formation of material crystals. The crystal growth and crystallization process was too short, and the crystals would become smaller as the cooling time shortened, and vice versa. Final repose angle: 55, the final repose angle index examples 6-10 were: 55, 54, 51, 57, 55, see Table 2 for details.

[0042] Table 2 Repose angle index of Examples 6-10

[0043] Stirring frequency Cooling time Drying equipment Controlling temperature Angle of repose Example 6 15HZ 1h triple 75℃ 55° Example 7 15HZ 1h triple 75℃ 54° Example 8 15HZ 1h triple 75℃ 51° Example 9 15HZ 1h triple 75℃ 57° Example 10 15HZ 1h triple 75℃ 55°

[0044] Example 11: A three-in-one (filter pressing, elution, drying in one) method for preparing avermectin wet powder, recrystallization method - three-in-one drying temperature demonstration:

[0045] (1) Using methanol to dissolve the crude avermectin, the speed of the crystallizer is adjusted to 30 Hz, and after heat preservation and dissolution, atmospheric distillation is performed. After concentration control, the temperature is lowered and the crystallization speed is 15 Hz. The cooling time is controlled to be 3 hours and the temperature is lowered to room temperature for pressure filtration. After pressure filtration, fine products are obtained one by one;

[0046] (2) adding methanol to the fine product of the first pass to dissolve it, repeating step (1) and filtering to obtain the fine product of the second pass;

[0047] (3) The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step (2) is repeated to obtain a third-pass crystallization liquid, which is then pressed into the three-in-one;

[0048] (4) The filtered crystal liquid obtained above is subjected to solid-liquid pressure filtration separation in a three-in-one device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is then filtered again to remove potential sugars and impurities carried by the material.

[0049] (5) The semi-finished product after the above-mentioned pressure filtration is subjected to mother fluid filtration, elution and stirring, and heating and drying in a three-in-one process, and the negative pressure drying is maintained. Then, the steam valve is adjusted to slowly heat the crystal to 85°C±1°C at a rate of 6-8°C / 10min for insulation, and then the temperature is lowered and the material is unloaded to obtain a wet fine product of avermectin with fluidity but small crystals, and the sample is sent for testing of the angle of repose of 53.

[0050] Using the process of this embodiment, the experiments of Examples 11-15 were also carried out. Five batches of experiments were arranged to carry out example demonstration. Since the processes of the five batches of experiments are exactly the same, the specific processes of Examples 11-15 will not be described in detail here.

[0051] Conclusion description: Although the subsequent drying equipment was replaced from double cone to three-in-one, and one more elution was added, the experiment proved that the three-in-one drying process temperature was too high, which would disperse the material crystals, reduce the crystal shape, and reduce the fluidity of the original material. This time, 5 batches of experiments were arranged for example demonstration. Since the 5 batches of experimental processes were exactly the same, the specific processes of Examples 11-15 are not described in detail here. The final repose angle indicators of Examples 11-15 were: 53, 50, 51, 52, and 52, respectively, as shown in Table 3.

[0052] Table 3 Repose angle index of Examples 11-15

[0053] Stirring frequency Cooling time Drying equipment Controlling temperature Angle of repose Embodiment 11 15HZ 3h triple 85℃ 53° Example 12 15HZ 3h triple 85℃ 50° Example 13 15HZ 3h triple 85℃ 51° Embodiment 14 15HZ 3h triple 85℃ 52° Embodiment 15 15HZ 3h triple 85℃ 52°

[0054] Example 16: A three-in-one (filter pressing, elution, drying in one) method for preparing avermectin wet powder, recrystallization method - demonstration after process optimization:

[0055] (1) Using methanol to dissolve the crude avermectin, the speed of the crystallizer is adjusted to 30 Hz, and after heat preservation and dissolution, atmospheric distillation is performed. After concentration control, the temperature is lowered and the crystallization speed is 15 Hz. The cooling time is controlled to be 3 hours and the temperature is lowered to room temperature for pressure filtration. After pressure filtration, fine products are obtained one by one;

[0056] (2) adding methanol to the fine product of the first pass to dissolve it, repeating step (1) and filtering to obtain the fine product of the second pass;

[0057] (3) The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step (2) is repeated to obtain a third-pass crystallization liquid, which is then pressed into the three-in-one;

[0058] (4) The filtered crystal liquid obtained above is subjected to solid-liquid pressure filtration separation in a three-in-one device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is then filtered again to remove potential sugars and impurities carried by the material.

[0059] (5) The semi-finished product after the above-mentioned pressure filtration is subjected to mother fluid filtration, elution and stirring, and heating and drying in a three-in-one process, and maintained under negative pressure drying. Then, the steam valve is adjusted to slowly heat the crystal to 75°C±1°C at a rate of 6-8°C / 10min for insulation, and then the temperature is lowered and unloaded to obtain a wet fine product of avermectin with fluidity and large crystals, and the sample is sent for testing of the angle of repose of 42.

[0060] Using the process of this embodiment, the experiments of Examples 16-35 were also carried out. This time, 20 batches of experiments were arranged to carry out example demonstration. Since the processes of the 20 batches of experiments are exactly the same, the specific processes of Examples 16-35 will not be described in detail here.

[0061] Conclusion description:

[0062] ① The cooling process of recrystallization control is adjusted to medium and low speed: 15HZ;

[0063] ②The cooling time is changed to slow cooling: 3h; thus completing the crystal growth and crystallization process;

[0064] ③ Use a three-in-one specific drying equipment to rinse the material;

[0065] ④Three-in-one heat preservation control temperature: 75℃±1℃, negative pressure drying;

[0066] The implementation of the above four measures ensures that the wet fine product of avermectin has the characteristics of large crystal shape and good fluidity. The demonstration test after process optimization is arranged to carry out 20 batches. Since the process requirements of the 20 batches of experiments are exactly the same, the specific processes of the batches of Examples 16-35 are not described in detail one by one here. The final repose angle index of Examples 16-35 are: 42, 38, 41, 37, 38, 36, 35, 35, 37, 34, 39, 38, 40, 41, 40, 39, 37, 38, 36, 37, see Table 4 for details).

[0067] Table 4 Repose angle index of Examples 16-35

[0068] Stirring frequency Cooling time Drying equipment Controlling temperature Angle of repose Example 16 15HZ 3h triple 85℃ 42° Embodiment 17 15HZ 3h triple 85℃ 38° Embodiment 18 15HZ 3h triple 85℃ 41° Embodiment 19 15HZ 3h triple 85℃ 37° Embodiment 20 15HZ 3h triple 85℃ 38° Embodiment 21 15HZ 3h triple 85℃ 36° Embodiment 22 15HZ 3h triple 85℃ 35° Embodiment 23 15HZ 3h triple 85℃ 35° Embodiment 24 15HZ 3h triple 85℃ 37° Embodiment 25 15HZ 3h triple 85℃ 34° Embodiment 26 15HZ 3h triple 85℃ 39° Embodiment 27 15HZ 3h triple 85℃ 38° Embodiment 28 15HZ 3h triple 85℃ 40° Embodiment 29 15HZ 3h triple 85℃ 41° Embodiment 30 15HZ 3h triple 85℃ 40° Embodiment 31 15HZ 3h triple 85℃ 39° Embodiment 32 15HZ 3h triple 85℃ 37° Embodiment 33 15HZ 3h triple 85℃ 38° Embodiment 34 15HZ 3h triple 85℃ 36° Embodiment 35 15HZ 3h triple 85℃ 37°

[0069] Comparative Example 1: A method for preparing a conventional wet fine product of avermectin (original double cone drying), comprising the following steps:

[0070] (1) The crude product of avermectin was dissolved in methanol by heat preservation, and the rotation speed of the crystallizer was adjusted to 30 Hz for atmospheric distillation. After concentration control, the crystallization was carried out by cooling, and the rotation speed was adjusted to 30 Hz, and the temperature was slowly lowered for 3 hours. After filter pressing, the fine product was obtained.

[0071] (2) The first-pass fine product obtained in step (1) is pumped back into the tank and methanol is added to dissolve it. The process of step (1) is repeated. The second-pass fine product is obtained after slow cooling and pressure filtration for 3 hours.

[0072] (3) The second-pass fine product obtained after the above (2) filter pressing is drawn back into the tank and methanol is added to dissolve, the crystallization tank speed is maintained at 30HZ, and carbon is added for filtration and dissolution, and then step (2) is repeated to obtain the third-pass fine product, which is pressed into the two-in-one;

[0073] (4) The cooled filtrate is pumped into a two-in-one device for solid-liquid separation. When no liquid flows out of the liquid outlet sight glass, the discharged material is weighed and then put into a double cone drying device. The steam valve is adjusted to maintain a negative pressure of 50°C for 1 hour, and then the temperature is reduced and the discharged material is discharged. The wet fine product of avermectin obtained by discharge has no fluidity. The sample is sent for inspection: the angle of repose is greater than 60.

[0074] Comparative Example 2: A method for preparing a conventional wet fine product of avermectin (original double cone drying), comprising the following steps:

[0075] (1) The crude product of avermectin was dissolved in methanol by heat preservation, and the rotation speed of the crystallizer was adjusted to 30 Hz for atmospheric distillation. After concentration control, the temperature was lowered for crystallization, and the rotation speed was adjusted to 15 Hz, and the temperature was slowly lowered for 1 hour. After filter pressing, the fine product was obtained.

[0076] (2) The first-pass fine product obtained in step (1) is pumped back into the tank and methanol is added to dissolve it. The process of step (1) is repeated. The second-pass fine product is obtained after slow cooling and pressure filtration for 3 hours.

[0077] (3) The second-pass fine product obtained after the above (2) filter pressing is drawn back into the tank and methanol is added to dissolve, the crystallization tank speed is maintained at 30HZ, and carbon is added for filtration and dissolution, and then step (2) is repeated to obtain the third-pass fine product, which is pressed into the two-in-one;

[0078] (4) The cooled filtrate is pumped into a two-in-one device for solid-liquid separation. When no liquid flows out of the liquid outlet sight glass, the discharged material is weighed and then put into a double cone drying device. The steam valve is adjusted to maintain a negative pressure of 50°C for 1 hour, and then the temperature is reduced and the discharged material is discharged. The wet fine product of avermectin obtained by discharge has no fluidity. The sample is sent for inspection: the angle of repose is greater than 60.

[0079] Comparative Example 3: A method for preparing a conventional wet fine product of avermectin (original double cone drying), comprising the following steps:

[0080] (1) The crude product of avermectin was dissolved in methanol by heat preservation, and the rotation speed of the crystallizer was adjusted to 30 Hz for atmospheric distillation. After concentration control, the temperature was lowered for crystallization, and the rotation speed was adjusted to 15 Hz, and the temperature was slowly lowered for 3 hours. After filter pressing, the fine product was obtained.

[0081] (2) The first-pass fine product obtained in step (1) is pumped back into the tank and methanol is added to dissolve it. The process of step (1) is repeated. The second-pass fine product is obtained after slow cooling and pressure filtration for 3 hours.

[0082] (3) The second-pass fine product obtained after the above (2) filter pressing is drawn back into the tank and methanol is added to dissolve, the crystallization tank speed is maintained at 30HZ, and carbon is added for filtration and dissolution, and then step (2) is repeated to obtain the third-pass fine product, which is pressed into the two-in-one;

[0083] (4) The cooled filtrate is pumped into a two-in-one device for solid-liquid separation. When no liquid flows out of the liquid outlet sight glass, the discharged material is weighed and then put into a double cone drying device. The steam valve is adjusted to maintain a negative pressure of 50°C for 1 hour, and then the temperature is reduced and the discharged material is discharged. The wet fine product of avermectin obtained by discharge has no fluidity. The sample is sent for testing: the angle of repose is 52.

[0084] Conclusion description: Keeping the double cone process, the recrystallization process was optimized successively, and 3 different batches were compared. Among them, comparative example 1 was a cooling speed of 30HZ, and a 3-hour cooling crystallization test. The conclusion was: no fluidity, and the repose angle was >60; comparative example 2 was a cooling speed of 15HZ, and the cooling was performed for 1h. The conclusion was: the material had a crystalline shape, but the crystals were small, relatively sticky, and had no fluidity, and the repose angle was >60; comparative example 3 was a cooling speed adjusted to 15HZ, and the cooling was performed slowly for 3h. The conclusion was: the material had a crystalline shape, but the crystals were small and slender, relatively flocculent and sticky, with slight fluidity, and the repose angle was 52. The final repose angle indicators of comparative examples 1-3 were: >60, >60, and 52, respectively. See Table 5 for details.

[0085] Table 5 Repose angle index of comparative examples 1-3

[0086] Stirring frequency Cooling time Drying equipment Controlling temperature Angle of repose Comparative Example 1 30HZ 3h Double cone 50℃ ＞60° Comparative Example 2 15HZ 1h Double cone 50℃ ＞60° Comparative Example 3 15HZ 3h Double cone 50℃ 52°

[0087] The present invention mainly solves the problem of fluidity of wet fine products of avermectin, and the angle of repose is an important indicator that effectively represents the fluidity. Based on the above embodiments and comparative examples, and taking the replacement of drying equipment as a prerequisite, process adjustment and data comparison analysis are carried out through Example Tables 1 to 4 (current drying equipment: three-in-one) and Comparative Table 5 (original drying equipment: double cone). The difference in the angle of repose shows that the lower the angle of repose index of the wet fine product of avermectin, the better the fluidity of its product. At the same time, it can be concluded from Example Tables 1 to 4 that the angle of repose index is affected by the stirring speed, cooling time, and negative pressure drying temperature during cooling crystallization. The process after reasonable optimization and adjustment can greatly improve the fluidity of the product (see Table 4 for details).

[0088] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing avermectin wet powder, characterized in that: The steps include: S1: Use methanol to dissolve the crude avermectin, keep it warm and dissolve it, then distill it at normal pressure, then cool it down and crystallize it after concentration control, then filter it at room temperature, and obtain fine products one by one after another after filter pressing; S2: Add methanol to dissolve the first-pass fine product, repeat step S1, and filter to obtain the second-pass fine product; S3: The second-pass fine product obtained after the filtration is further supplemented with methanol for carbon filtration and dissolution, and then step S2 is repeated to obtain a third-pass crystallization liquid, which is pressed into a filter drying device; S4: The obtained crystal liquid after filtration is subjected to solid-liquid filtration separation in a filter drying device. After the filtration is completed, methanol is added for pulping and washing to thoroughly wash the material and make it white. The material is filtered again to remove potential sugars and impurities carried by the material. S5: The semi-finished product after the filter press is filtered by the mother fluid, rinsed and stirred, and heated and dried in the filter drying equipment, and the negative pressure is maintained for drying. Then the steam valve is adjusted, and the crystal is slowly heated up and then kept warm. After that, the temperature is lowered and the material is unloaded to obtain the avermectin wet powder with large crystals and fluidity.

2. The method for preparing a wet-powder of avermectin as claimed in claim 1, wherein: After dissolution in S1, the rotation speed of the crystallization tank is adjusted to 30HZ.

3. The method for preparing a kind of avermectin wet powder as claimed in claim 1, characterized in that, After cooling and crystallization in S1, the rotation speed is adjusted to 15HZ-30HZ.

4. The method for preparing a kind of avermectin wet powder as claimed in claim 1, characterized in that, The cooling time in S1 is controlled to be 3h.

5. The method for preparing a kind of avermectin wet powder as claimed in claim 1, characterized in that, In the S3, charcoal is added for filtration and decolorization, and the cooling time is controlled to be 3 hours, and the cooling speed is 15 Hz to obtain three crystallization solutions.

6. The method for preparing a kind of avermectin wet powder as claimed in claim 1, characterized in that, The regulating steam valve slowly raises the temperature to 75°C-85°C at a rate of 6-8°C / 10min for heat preservation.