A system for recovering acidic waste liquid of pendimethalin

Abstract

This invention relates to the field of pesticide production wastewater treatment technology, and particularly to a dimethoate acidic wastewater recovery system, which overcomes the shortcomings of existing technologies. The system includes a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit, and a central control unit. The outlet of the pretreatment unit is connected to the inlet of the multi-stage extraction unit, and the pretreatment unit includes a pH adjustment tank, a filter, and a storage tank. The multi-stage extraction unit employs a three-stage countercurrent extraction tower, and its outlet is connected to the inlet of the separation and purification unit. The separation and purification unit includes a falling film evaporator and a molecular distillation device, and its outlet is connected to the solvent recovery unit, which includes a plate condenser and a distillation column. Compared with existing technologies, this invention effectively reduces energy consumption and cost, and improves recovery rate and loss rate.

Description

Technical Field

[0001] This invention relates to the field of pesticide production wastewater treatment technology, and in particular to a dimethoate acid wastewater recovery system. Background Technology

[0002] Pendimethalin is a widely used herbicide in agriculture, and its production process often generates acidic wastewater. This wastewater typically contains unreacted raw materials, byproducts, acidic catalysts (such as sulfuric acid and hydrochloric acid), and small amounts of pendimethalin residue, characterized by high acidity, high chemical oxygen demand (COD), and recalcitrant organic matter. Direct discharge of this wastewater not only causes serious environmental pollution but also leads to the waste of valuable resources.

[0003] Currently, the main methods for treating dimethyl pendimethalin acidic waste liquid include neutralization, incineration, and biological treatment, but these methods have the following limitations:

[0004] Neutralization method: The pH of the waste liquid is adjusted by adding alkaline solution, but it produces a large amount of sludge and cannot recover valuable components, resulting in high treatment costs.

[0005] Incineration: High energy consumption and may produce secondary pollutants (such as dioxins), making it less economically viable.

[0006] Biological treatment: Due to the inhibitory effect of high concentrations of organic matter and acidic substances in the waste liquid, the microbial degradation efficiency is low and the treatment cycle is long.

[0007] Furthermore, existing technologies have low recovery rates for useful components (such as pendimethalin, solvents, or acidic catalysts) in waste liquids, failing to achieve resource recycling. Therefore, we propose a pendimethalin acidic waste liquid recovery system to address the aforementioned problems. Summary of the Invention

[0008] The purpose of this invention is to provide a dimethyl pendimethalin acidic waste liquid recovery system to solve the problems mentioned in the background art.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0010] A dimethoate acidic waste liquid recovery system includes a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit, and a central control unit. The outlet of the pretreatment unit is connected to the inlet of the multi-stage extraction unit, and the pretreatment unit includes a pH adjustment tank, a filter, and a storage tank. The multi-stage extraction unit adopts a three-stage countercurrent extraction tower, and the outlet of the multi-stage extraction unit is connected to the inlet of the separation and purification unit. The separation and purification unit includes a falling film evaporator and a molecular distillation device, and the outlet of the separation and purification unit is connected to the solvent recovery unit, which includes a plate condenser and a distillation column.

[0011] The pretreatment unit, multi-stage extraction unit, separation and purification unit, and solvent recovery unit are all connected and controlled by the central control unit.

[0012] In one embodiment, the stirring rate of the pH adjusting tank is 200–400 rpm, the filter accuracy is 5–10 μm, the working pressure of the filter is 0.4–0.6 MPa, and the storage tank is located between the pH adjusting tank and the filter.

[0013] In one embodiment, the interior of the three-stage countercurrent extraction tower is filled with polytetrafluoroethylene corrugated packing, and the extraction temperature is maintained at 25–35°C.

[0014] In one embodiment, the extractant used in the three-stage countercurrent extraction tower is a mixed solution of cyclohexanone and n-octanol in a volume ratio of 3:2 to 4:1, wherein 0.1 to 0.3% of a demulsifier is added to the total mass of the mixed solution.

[0015] In one embodiment, in the three-stage countercurrent extraction tower, the extraction ratio for the first stage is 1:4 to 1:5, the extraction ratio for the second stage is 1:2 to 1:3, and the extraction ratio for the third stage is 1:1 to 1:1.5.

[0016] In one embodiment, the pressure of the falling film evaporator is -0.08 to -0.095 MPa, the heating temperature is 60 to 80°C, the evaporation surface temperature of the molecular distillation equipment is 80 to 120°C, and the condensation surface temperature is -10 to -5°C.

[0017] In one embodiment, the heat exchange area of ​​the plate condenser is 20–30 m². 2 .

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0019] 1. This system combines three-stage countercurrent extraction with molecular distillation, which improves the recovery rate in the extraction stage while reducing the loss rate in the distillation stage.

[0020] 2. This system uses a falling film evaporator instead of traditional distillation, and employs a staged neutralization process of first sodium bicarbonate and then sodium hydroxide during pH adjustment, which reduces processing costs and energy consumption. Attached Figure Description

[0021] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0022] In the attached diagram:

[0023] Figure 1 This is a schematic diagram of the overall process of the present invention. Detailed Implementation

[0024] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0025] Please see Figure 1 The present invention provides the following technical solution:

[0026] A dimethoate acidic waste liquid recovery system includes a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit, and a central control unit. The outlet of the pretreatment unit is connected to the inlet of the multi-stage extraction unit.

[0027] The pretreatment unit includes a pH adjustment tank, a filter, and a storage tank. The stirring rate of the pH adjustment tank is 200-400 rpm, the filter accuracy is 5-10 μm, the working pressure of the filter is 0.4-0.6 MPa, and the storage tank is located between the pH adjustment tank and the filter, and the inner lining of the storage tank is coated with a polypropylene anti-corrosion layer.

[0028] It should be further explained that the waste liquid with pH 1.5 to 3.0 first enters the pH adjustment tank, and after passing through the fractional neutralization process of sodium bicarbonate and sodium hydroxide, it is adjusted to 4.0 to 5.0 before flowing into the storage tank. Then, it is filtered to remove impurities before being discharged.

[0029] The multi-stage extraction unit adopts a three-stage countercurrent extraction tower, and the outlet of the multi-stage extraction unit is connected to the inlet of the separation and purification unit. The interior of the three-stage countercurrent extraction tower is filled with polytetrafluoroethylene corrugated packing. The extraction temperature is maintained at 25-35℃. The extractant used in the three-stage countercurrent extraction tower is a mixed solution of cyclohexanone and n-octanol in a volume ratio of 3:2 to 4:1, wherein 0.1-0.3% of the total mass of the mixed solution is added as a demulsifier.

[0030] It should be further noted that the three-stage countercurrent extraction was carried out at a temperature of 25–35°C, with the first-stage extraction ratio being 1:4–1:5, the second-stage extraction ratio being 1:2–1:3, and the third-stage extraction ratio being 1:1–1:1.5, and the extraction time being 30–50 min.

[0031] The separation and purification unit includes a falling film evaporator and a molecular distillation device. The outlet of the separation and purification unit is connected to the solvent recovery unit. The pressure of the falling film evaporator is -0.08 to -0.095 MPa, and the heating temperature is 60 to 80°C. The evaporation surface temperature of the molecular distillation device is 80 to 120°C, and the condensation surface temperature is -10 to -5°C.

[0032] It should be further explained that the waste liquid after extraction is preheated to 50-60℃ (to reduce viscosity). Under the action of a rotating scraper (the scraper rotor speed is 150-200 rpm), the waste liquid forms an extremely thin liquid film (thickness is 0.1-0.3 mm, evaporation time is controlled at 10-15 seconds to avoid thermal decomposition). The vaporized dimethyl pendimethalin is rapidly liquefied at the -10℃ condensation surface and collected into the product tank, while the unevaporated high-boiling-point substances (containing dimethyl pendimethalin <2%) are continuously discharged through the bottom screw conveyor.

[0033] The solvent recovery unit includes a plate condenser and a distillation column. The heat exchange area of ​​the plate condenser is 20–30 m². 2 .

[0034] It should be further noted that the solvent vapor from the separated and purified waste liquid is condensed in a plate condenser (heat exchange area 25m²). 2 The condensate is liquefied and the temperature drops below 25°C. The condensate enters an automatic stratification tank, where trace amounts of water are separated by density difference (discharge is controlled by an interface capacitance sensor). The solvent is pumped into a distillation column, and a cyclohexanone / n-octanol mixture with a purity ≥99.5% is collected at the top of the column. Dimethylpentylene is recovered at the outlet of the distillation column.

[0035] The pretreatment unit, multi-stage extraction unit, separation and purification unit, and solvent recovery unit are all connected and controlled by the central control unit.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection, the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the meaning of the above terms in this application according to the specific circumstances.

[0037] The above provides a detailed description of a dimethoate acidic waste liquid recovery system provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A dimethoate acidic waste liquid recovery system, comprising a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit, and a central control unit, characterized in that, The outlet of the pretreatment unit is connected to the inlet of the multi-stage extraction unit, and the pretreatment unit includes a pH adjustment tank, a filter and a storage tank. The multi-stage extraction unit adopts a three-stage countercurrent extraction tower. The outlet of the multi-stage extraction unit is connected to the inlet of the separation and purification unit, which includes a falling film evaporator and a molecular distillation device. The outlet of the separation and purification unit is connected to the solvent recovery unit, which includes a plate condenser and a distillation column. The waste liquid solvent vapor obtained from the separation and purification unit enters the plate condenser for condensation. The condensate is then transported to the automatic separation tank, and the organic phase in the automatic separation tank is transported to the feed inlet of the distillation column by the solvent pump. The pretreatment unit, multi-stage extraction unit, separation and purification unit, and solvent recovery unit are all connected and controlled by the central control unit. The extractant used in the three-stage countercurrent extraction tower is a mixed solution of cyclohexanone and n-octanol in a volume ratio of 3:2 to 4:1, wherein 0.1 to 0.3% of a demulsifier is added to the total mass of the mixed solution. The pressure of the falling film evaporator is -0.08 to -0.095 MPa, the heating temperature is 60 to 80°C, the evaporation surface temperature of the molecular distillation equipment is 80 to 120°C, and the condensation surface temperature is -10 to -5°C.

2. The dimethoate acid waste liquid recovery system according to claim 1, characterized in that, The stirring rate of the pH adjusting tank is 200-400 rpm, the filter accuracy is 5-10 μm, the working pressure of the filter is 0.4-0.6 MPa, and the storage tank is located between the pH adjusting tank and the filter.

3. The dimethoate acid waste liquid recovery system according to claim 1, characterized in that, The interior of the three-stage countercurrent extraction tower is filled with polytetrafluoroethylene corrugated packing, and the extraction temperature is maintained at 25-35℃.

4. The dimethoate acid waste liquid recovery system according to claim 1, characterized in that, In the three-stage countercurrent extraction tower, the extraction ratio for the first stage is 1:4 to 1:5, the extraction ratio for the second stage is 1:2 to 1:3, and the extraction ratio for the third stage is 1:1 to 1:1.

5.

5. The dimethoate acid waste liquid recovery system according to claim 1, characterized in that, The heat exchange area of ​​the plate condenser is 20-30 m².

Images