Pendimethalin acid waste liquid recovery system

Abstract

The invention relates to the technical field of pesticide production waste liquid treatment, in particular to a pendimethalin acid waste liquid recovery system which overcomes the defects in the prior art and comprises a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit and a central control unit. An outlet of the pretreatment unit is connected with an inlet of the multi-stage extraction unit, the pretreatment unit comprises a pH adjusting tank, a filter and a storage tank, the multi-stage extraction unit adopts a three-stage counter-current extraction tower, and an outlet of the multi-stage extraction unit is connected with an inlet of the separation and purification unit; the separation and purification unit comprises a falling film evaporator and molecular distillation equipment, an outlet of the separation and purification unit is connected with the solvent recovery unit, and the solvent recovery unit comprises a plate-type condenser and a rectifying tower. Compared with the prior art, the treatment energy consumption and cost are effectively reduced, and the recovery rate and the loss rate are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pesticide production waste liquid treatment, and particularly relates to a pendimethalin acidic waste liquid recovery system. BACKGROUND

[0002] Pendimethalin is a widely used herbicide in agriculture. Its production process is often accompanied by the generation of acidic waste liquid. These waste liquids usually contain unreacted raw materials, by-products, acidic catalysts (such as sulfuric acid, hydrochloric acid, etc.) and a small amount of pendimethalin residues, and have characteristics such as high acidity, high chemical oxygen demand (COD) and refractory organic matter. If directly discharged, it will not only cause serious environmental pollution, but also lead to waste of useful resources.

[0003] At present, the treatment methods for pendimethalin acidic waste liquid mainly include neutralization method, incineration method, biological treatment method, etc., but these methods have the following limitations:

[0004] Neutralization method: by adding alkali solution to adjust the pH of the waste liquid, but a large amount of sludge will be generated, and valuable components cannot be recovered, and the treatment cost is high.

[0005] Incineration method: high energy consumption, and may produce secondary pollutants (such as dioxins), poor economic efficiency.

[0006] Biological treatment method: due to the inhibitory effect of high-concentration organic matter and acidic substances in the waste liquid, the microbial degradation efficiency is low, and the treatment period is long.

[0007] In addition, the existing technology has low recovery and utilization rate of valuable components (such as pendimethalin, solvent or acidic catalyst) in the waste liquid, and fails to realize the recycling of resources. Therefore, we propose a pendimethalin acidic waste liquid recovery system to solve the above problems. SUMMARY

[0008] The purpose of the present application is to provide a pendimethalin acidic waste liquid recovery system to solve the problems raised in the background art.

[0009] In order to solve the above technical problems, the present application provides the following technical scheme:

[0010] A pendimethalin 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, the outlet of the pretreatment unit is connected with the inlet of the multi-stage extraction unit, and the pretreatment unit comprises a pH adjusting 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 with the inlet of the separation and purification unit, the separation and purification unit comprises a falling film evaporator and a molecular distillation device, the outlet of the separation and purification unit is connected with the solvent recovery unit, and the solvent recovery unit comprises a plate condenser and a rectification tower.

[0011] The pre-treatment unit, the multi-stage extraction unit, the separation and purification unit and the 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 precision of the filter is 5-10 microns, the working pressure of the filter is 0.4-0.6 MPa, and the storage tank is arranged 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℃.

[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 3:2-4:1, and 0.1-0.3% of the total mass of the mixed solution is added as a demulsifier.

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

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

[0017] In one embodiment, the heat exchange area of the plate condenser is 20-30 m 2 .

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. The system uses a combination process of three-stage countercurrent extraction and molecular distillation to improve the recovery rate in the extraction stage and reduce the loss rate in the distillation stage.

[0020] 2. The system uses a falling film evaporator to replace the traditional distillation, and uses a staged neutralization of sodium bicarbonate followed by sodium hydroxide in the pH adjustment process, which reduces the processing cost and energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0021] The technical solutions and other beneficial effects of the present application will become apparent from the following detailed description of specific embodiments of the present application, combined with the accompanying drawings.

[0022] In the drawings:

[0023] Figure 1 is the overall process schematic diagram of the present application. DETAILED DESCRIPTION

[0024] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplicity, the elements and settings of the particular examples in the following description are set forth by way of illustrations. For example, the purpose of this disclosure is not in anyway limited to the particular examples described herein. In addition, the disclosure can repeat reference numerals and / or letters in the various examples and this repetition is for the purpose of simplicity and clarity and does not in way indicate a relationship between the various embodiments and / or settings discussed. Moreover, the principles of the present application can be used to implement various embodiments and / or examples.

[0025] Referring now to the drawings Figure 1 The present application provides technical solutions:

[0026] The system comprises a pretreatment unit, a multi-stage extraction unit, a separation and purification unit, a solvent recovery unit and a central control unit.

[0027] The pretreatment unit comprises a pH adjusting tank, a filter and a storage tank, the stirring rate of the pH adjusting tank is 200-400 rpm, the precision of the filter is 5-10 microns, the working pressure of the filter is 0.4-0.6 MPa, and the storage tank is arranged between the pH adjusting tank and the filter, and the inner lining of the storage tank is coated with a polypropylene corrosion-resistant layer.

[0028] It should be further pointed out that the waste liquid with pH 1.5-3.0 first enters the pH adjusting tank, and then is subjected to a staged neutralization process of sodium bicarbonate and sodium hydroxide, and then is adjusted to 4.0-5.0, and then flows into the storage tank, and then is discharged after removing the impurity particles in the filter.

[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 three-stage countercurrent extraction tower is internally filled with polytetrafluoroethylene corrugated packing, the extraction temperature is maintained at 25-35℃, and the extraction agent used in the three-stage countercurrent extraction tower is a mixed solution of cyclohexanone and n-octanol in a volume ratio of 3:2-4:1, wherein 0.1-0.3% of the total mass of the mixed solution is added as a demulsifier.

[0030] It should be further pointed out that the three-stage countercurrent extraction is carried out at a temperature of 25-35℃, wherein the phase ratio of the first-stage extraction is 1:4-1:5, the phase ratio of the second-stage extraction is 1:2-1:3, and the phase ratio of the third-stage extraction is 1:1-1:1.5, and the extraction time is 30-50 min.

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

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

[0033] The solvent recovery unit comprises a plate condenser and a rectification tower, the heat exchange area of the plate condenser is 20 to 30 m 2 .

[0034] It should be further explained that the waste liquid solvent vapor after separation and purification is liquefied through a plate condenser (the heat exchange area is 25 m 2 ), the temperature is reduced to below 25 DEG C, the condensate enters an automatic delamination tank, trace water is separated by using the density difference (an interface capacitance sensor controls the discharge), the solvent is pumped into the rectification tower, the mixed liquid of cyclohexanone / n-octanol with a purity of ≥ 99.5% is collected at the top of the tower, and dimethenamid is recovered at the outlet of the rectification tower.

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

[0036] In the description of the present application, it should be explained that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected or can be in communication with each other; it can be directly connected, or it can be the communication or interaction relationship between two elements. For those skilled in the art, the meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] The above has carried on the detailed introduction to the system for recycling of pendimethalin acid waste liquid provided by the embodiment of the application, the principle and implementation mode of the application are described by applying specific examples in the paper, the above embodiment is only used for helping understanding the technical scheme of the application and its core idea; the ordinary skilled in the art should understand that: it can still modify the technical scheme recorded by the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical scheme deviate from the scope of the technical scheme of the embodiments of the application.

Claims

1. A system for recovering acidic waste liquid of pendimethalin, comprising a pretreatment unit, a multistage 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 with the inlet of the multi-stage extraction unit, the pretreatment unit comprises a pH adjusting 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 with the inlet of the separation and purification unit, the separation and purification unit comprises a falling film evaporator and a molecular distillation device, the outlet of the separation and purification unit is connected with the solvent recovery unit, and the solvent recovery unit comprises a plate condenser and a rectifying tower. The pretreatment unit, the multi-stage extraction unit, the separation and purification unit and the solvent recovery unit are all controlled by the central control unit.

2. The system for recovering acidic prid acid waste liquid according to claim 1, wherein The stirring speed of the pH adjusting tank is 200-400 rpm, the precision of the filter is 5-10 microns, the working pressure of the filter is 0.4-0.6 MPa, and the storage tank is arranged between the pH adjusting tank and the filter.

3. The system for recovering the acidic prid acid waste liquid according to claim 1, wherein The three-stage countercurrent extraction tower is internally filled with polytetrafluoroethylene corrugated packing, and the extraction temperature is kept at 25-35 DEG C.

4. The system for recovering the acidic prid acid waste liquid according to claim 3, characterized in that, The extraction agent used in the three-stage countercurrent extraction tower is a mixed solution of cyclohexanone and n-octanol in a volume ratio of 3:2-4:1, wherein 0.1-0.3% of the total mass of the mixed solution is added as a demulsifier.

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

5.

6. The system for recovering the acidic prid acid waste liquid according to claim 1, wherein The pressure of the falling film evaporator is -0.08--0.095 MPa, the heating temperature is 60-80 DEG C, the evaporation surface temperature of the molecular distillation device is 80-120 DEG C, and the condensation surface temperature is -10--5 DEG C.

7. The system for recovering the acidic prid acid waste liquid according to claim 1, wherein The heat exchange area of the plate condenser is 20-30 m 2 .

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