CN109627170B - Method for extracting polynitrotoluene from nitrotoluene acidic wastewater - Google Patents
Method for extracting polynitrotoluene from nitrotoluene acidic wastewater Download PDFInfo
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- CN109627170B CN109627170B CN201811544908.3A CN201811544908A CN109627170B CN 109627170 B CN109627170 B CN 109627170B CN 201811544908 A CN201811544908 A CN 201811544908A CN 109627170 B CN109627170 B CN 109627170B
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/16—Separation; Purification; Stabilisation; Use of additives
Abstract
The invention relates to the technical field of nitrotoluene preparation, in particular to a method for extracting polynitrotoluene from nitrotoluene acidic wastewater, which comprises the steps of mixing mononitrotoluene, acidic wastewater, mixed nitrates in a collecting tank and refluxed emulsified acidic water by using a delivery pump, delivering the mixture to a cooler for cooling twice, then carrying out primary separation on liquid to obtain mixed nitrates and acidic water, carrying out secondary separation on the acidic water to obtain mixed nitrates, clarified acidic water and emulsified acidic water, flowing the clarified acidic water into a wastewater treatment system for treatment, refluxing and delivering the emulsified acidic water to the delivery pump, wherein the primary separation is gravity settling separation, the secondary separation is gravity settling separation after filtration, the mixed nitrates obtained by the primary separation and the secondary separation are stored in the collecting tank, part of the mixed nitrates is delivered to the delivery pump, and the other mixed nitrates are extracted polynitrotoluene products, the method reduces the content of the nitro compound in the wastewater, and is economical, environment-friendly, safe and convenient.
Description
Technical Field
The invention relates to the technical field of nitrotoluene preparation, in particular to a method for extracting polynitrotoluene from nitrotoluene acidic wastewater.
Background
Nitrotoluene is one of the components of common explosives, and explosive enterprises generate a large amount of acidic wastewater containing nitrotoluene and sulfuric acid in daily nitration production, wherein nitrotoluene compounds comprise mononitrotoluene, dinitrotoluene and trinitrotoluene, and the dinitrotoluene and the trinitrotoluene have high contents, are toxic and difficult to biodegrade, and have certain difficulty in wastewater treatment.
At present, the main domestic nitrotoluene wastewater treatment methods comprise a chlorine dioxide oxidation and catalytic oxidation method, a micro-electrolysis, oxidation, anaerobic and aerobic biochemical treatment method, an incineration treatment method and a vacuum concentration treatment method, wherein a QVF vacuum concentration treatment technology is an advanced treatment process at present, the technology carries out vacuum concentration on wastewater in different stages in the nitrotoluene production process and then extracts nitrotoluene compounds, wherein two-stage wastewater generates acid wastewater with high temperature of about 60 ℃, three-stage wastewater generates acid wastewater with about 20 ℃, the content of dinitrotoluene in the acid wastewater with high temperature of 60 ℃ reaches 1500mg/L, the content of dinitrotoluene in the acid wastewater with 20 ℃ reaches 90mg/L-100mg/L, and the content of trinitrotoluene reaches 100mg/L-110 mg/L.
In order to further treat the acid wastewater subjected to vacuum concentration, in the prior art, the acid wastewater with high temperature of 60 ℃ is cooled and cooled in a larger cooling and precipitating tank, the solubility of di-nitrotoluene and trinitrotoluene is reduced after cooling, so that part of di-nitrotoluene and trinitrotoluene is precipitated and precipitated to the bottom of the tank, the treated acid wastewater contains 450mg/L-500mg/L of dinitrotoluene and 50mg/L-80mg/L of trinitrotoluene, and then the acid wastewater enters a wastewater treatment device for treatment. The solid di-and trinitrotoluenes and derivatives in the sedimentation basin require manual cleaning, which is dangerous.
Disclosure of Invention
The invention aims to provide a method for extracting polynitrotoluene from nitrotoluene acidic wastewater, which utilizes the fact that the solubility of mononitrotoluene is less than that of dinitrotoluene and trinitrotoluene, thereby replacing di-nitrotoluene and trinitrotoluene from the wastewater, emulsifying the mononitrotoluene and separating the emulsified mononitrotoluene from the wastewater, thereby reducing the content of nitrated substances in the wastewater.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for extracting polynitrotoluene from nitrotoluene acidic wastewater comprises the steps of mixing mononitrotoluene, acidic wastewater, mixed nitrates in a collecting tank and backflow emulsified acidic water by a delivery pump, delivering the mixture to a cooler for cooling twice, reducing the temperature of liquid to be lower than 20 ℃, enabling the acidic wastewater to comprise high-temperature acidic wastewater and low-temperature acidic wastewater generated by vacuum concentration, then carrying out primary separation on the liquid to obtain mixed nitrates and acidic water, carrying out secondary separation on the acidic water to obtain mixed nitrates, clarified acidic water and emulsified acidic water, enabling the clarified acidic water to flow into a wastewater treatment system for treatment, enabling the emulsified acidic water to flow back to the delivery pump, carrying out primary separation as gravity settling separation, carrying out secondary separation as gravity settling separation after filtration, storing the mixed nitrates obtained by the primary separation and the secondary separation in the collecting tank, delivering part of the mixed nitrates to the delivery pump, the other mixed nitrated compound is the extracted polynitrotoluene product.
Preferably, the dosing ratio of the mononitrotoluene into the transfer pump is controlled by a control valve.
Preferably, the adding proportion of the mononitrotoluene is 0.5 to 1 percent of the total inflow rate of the acidic wastewater and the emulsified acidic water.
Preferably, when the temperature is reduced in the cooler, the first temperature reduction is realized by using circulating water, the liquid temperature is reduced to be lower than 40 ℃, and the second temperature reduction is realized by using chilled water at the temperature of 7-12 ℃.
Preferably, the second temperature reduction is performed by using 7 ℃ frozen water.
And in the secondary separation, a hydrophilic filter screen is used for filtering to obtain clear acidic water and emulsified acidic water containing the mixed nitrated substance, and then the emulsified acidic water containing the mixed nitrated substance is subjected to gravity settling separation to obtain the mixed nitrated substance and the emulsified acidic water.
Preferably, the aperture of the mesh of the hydrophilic filter screen is 20-30 μm.
Preferably, the transfer pump is a centrifugal pump.
The invention has the beneficial effects that: firstly, mononitrotoluene is liquid at normal temperature, dinitrotoluene and trinitrotoluene are solid at normal temperature, in the prior art, the main nitrites in the wastewater are dinitrotoluene and trinitrotoluene, it is dissolved in sulfuric acid, the solubility is reduced after temperature reduction to precipitate solid crystals, the content of mononitrotoluene is improved in the technology, dinitrotoluene and trinitrotoluene are dissolved in mononitrotoluene, because of the existence of mononitrotoluene, the solubility of dinitrotoluene and trinitrotoluene in the wastewater is reduced, so that the di-nitrotoluene and the trinitrotoluene are mainly dissolved in the mononitrotoluene, and the nitride is separated from the acid washing wastewater due to different specific gravities, thus, the method can obtain mixed nitride and acidic water after primary separation, the content of the nitride in the acidic water is reduced to be below 100mg/L, mononitrotoluene in the nitride accounts for the main part, and the content of trinitrotoluene is close to 0.
Secondly, the toxicity of nitro compounds to biological bacteria is ranked as: the technical scheme is that mononitrotoluene is added, so that the content of dinitrotoluene and trinitrotoluene in the wastewater is greatly reduced, and low-toxicity substances are used for replacing high-toxicity substances.
Thirdly, in the technical scheme, the mixed liquid is stirred and flows through the pump, the mononitrotoluene is emulsified, the mononitrotoluene can be separated out during secondary separation, mixed nitrates, clarified acidic water and emulsified acidic water are obtained through separation, the emulsified acidic water is used as a raw material again and enters circulation, the product obtained by the technical scheme only comprises the mixed nitrates and the clarified acidic water, the mixed nitrates can be recycled and then processed into a product, the content of nitro compounds in the clarified acidic water is very low and can enter a wastewater biochemical treatment system, the content of the di-nitrotoluene and the trinitrotoluene in the acidic wastewater entering the wastewater biochemical treatment system are greatly reduced, the toxicity of the acidic wastewater is greatly reduced, the biochemical treatment of the wastewater is facilitated, and the treatment capacity of an acidic wastewater device is improved.
Fourthly, in the technical scheme, the liquid mononitrotoluene is adopted to extract the di-and trinitrotoluene which can be crystallized originally, so that the mandatory cooling of the acid wastewater is simplified from complexity.
Fifth, in economic terms, the technology can reduce the investment scale by 1 large cooling sedimentation tank compared with the prior art, and does not need to clean dangerous solid photochemical nitrotoluene derivatives.
Sixth, no daily field operators are required.
The value of the nitrotoluene recovered by the invention can balance the daily operation cost, and the cost is 50-80 ten thousand yuan beyond the annual saving cost of reducing the cleaning cost of a cooling sedimentation tank and the like due to the improvement of the wastewater treatment capacity, so that the biochemical treatment of the acidic wastewater is easy, and the final discharge index after the wastewater treatment is improved.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the scope of the present invention is not limited thereto.
The method for extracting polynitrotoluene from nitrotoluene acidic wastewater of the embodiment comprises the steps of mixing and conveying mononitrotoluene, acidic wastewater, mixed nitrates in a collecting tank and refluxed emulsified acidic water to a cooler by using a conveying pump, cooling the mixed nitrates and the emulsified acidic water for two times, reducing the temperature of liquid to be lower than 20 ℃, wherein the acidic wastewater comprises high-temperature acidic wastewater and low-temperature acidic wastewater generated by vacuum concentration, then performing primary separation on the liquid to obtain mixed nitrates and acidic water, performing secondary separation on the acidic water to obtain mixed nitrates, clarified acidic water and emulsified acidic water, flowing the clarified acidic water into a wastewater treatment system for treatment, refluxing and conveying the emulsified acidic water to the conveying pump, performing primary separation for gravity settling separation, performing secondary separation for gravity settling separation after filtration, storing the mixed nitrates obtained by the primary separation and the secondary separation in the collecting tank, and conveying part of the mixed nitrates to the conveying pump, the other mixed nitrated compound is the extracted polynitrotoluene product.
The temperature of the waste water after cooling is lower than 20 ℃, which is determined according to the solubility of the nitro compound and the economic efficiency, and can be a slightly higher temperature or a lower temperature, such as 25 ℃ and 10 ℃. The equilibrium solubility of dinitrotoluene in the acid wastewater is 1500mg/L at the temperature of 60 ℃, the solubility of dinitrotoluene in water is about 370mg/L at the temperature of 20 ℃, and the content of mononitrotoluene in the vacuum concentration two-stage acid wastewater is 70mg/L-100mg/L at the temperature of 20 ℃ (the solubility of mononitrotoluene in water is not found in the publication, and the data is the test data of the company).
Furthermore, the adding proportion of the mononitrotoluene entering the delivery pump is controlled by a control valve, the adding proportion of the mononitrotoluene is 0.5% -1% of the total inflow of the acidic wastewater and the emulsified acidic water, the adding proportion of the mononitrotoluene can be larger, when the adding proportion of the mononitrotoluene is 1% -2%, the separation speed of secondary separation needs to be adjusted, and the adding proportion of the mononitrotoluene is reduced, when the adding proportion of the mononitrotoluene is 0.2% -0.5%, the separation efficiency is reduced.
Furthermore, when the temperature is reduced in the cooler, the temperature of the liquid is reduced to be lower than 40 ℃ by using circulating water for the first time, the temperature of the liquid is reduced by using chilled water at the temperature of 7-12 ℃ for the second time, and the temperature of the chilled water at the temperature of 7 ℃ is preferably reduced for the second time.
Further, in the secondary separation, a hydrophilic filter screen is used for filtering to obtain clear acidic water and emulsified acidic water containing the mixed nitrated substance, and then the emulsified acidic water containing the mixed nitrated substance is subjected to gravity settling separation to obtain the mixed nitrated substance and the emulsified acidic water.
Furthermore, the aperture of the mesh of the hydrophilic filter screen is 20-30 μm.
Further, the delivery pump is a centrifugal pump, and the mononitrotoluene is rapidly emulsified by strong stirring of the centrifugal pump.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (8)
1. The method for extracting the polynitrotoluene from the nitrotoluene acidic wastewater is characterized by comprising the following steps: mixing mononitrotoluene, acid wastewater, mixed nitrates in a collecting tank and refluxed emulsified acid water by using a conveying pump, conveying the mixture to a cooler for cooling twice, reducing the liquid temperature to be lower than 20 ℃, wherein the acid wastewater is two-section wastewater and three-section wastewater which are generated after a nitrotoluene compound is extracted by vacuum concentration of wastewater in a nitrotoluene production process by adopting a QVF vacuum concentration treatment technology, the two-section wastewater is high-temperature acid wastewater, the three-section wastewater is low-temperature acid wastewater, then the liquid is subjected to primary separation to obtain the mixed nitrates and the acid water, the acid water is subjected to secondary separation to obtain the mixed nitrates, clarified acid water and emulsified acid water, the clarified acid water flows into a wastewater treatment system for treatment, the emulsified acid water is conveyed to the conveying pump in a refluxing manner, the primary separation is gravity settling separation, the secondary separation is gravity settling separation after filtration, and storing the mixed nitride obtained by the primary separation and the secondary separation in a collecting tank, conveying part of the mixed nitride to a conveying pump, and taking other mixed nitrides as the extracted polynitrotoluene product.
2. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 1, wherein: the adding proportion of the mononitrotoluene entering the delivery pump is controlled by a control valve.
3. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 2, characterized in that: the adding proportion of the mononitrotoluene is 0.5 to 1 percent of the total inflow flow of the acidic wastewater and the emulsified acidic water.
4. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 1, wherein: when the temperature is reduced in the cooler, the first temperature reduction uses circulating water to reduce the temperature, the liquid temperature is reduced to be lower than 40 ℃, and the second temperature reduction uses 7-12 ℃ chilled water to reduce the temperature.
5. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 1, wherein: the second temperature reduction is carried out by using frozen water with the temperature of 7 ℃.
6. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 1, wherein: and in the secondary separation, a hydrophilic filter screen is used for filtering to obtain clear acidic water and emulsified acidic water containing the mixed nitrated substance, and then the emulsified acidic water containing the mixed nitrated substance is subjected to gravity settling separation to obtain the mixed nitrated substance and the emulsified acidic water.
7. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 6, wherein: the aperture of the mesh of the hydrophilic filter screen is 20-30 mu m.
8. The method for extracting polynitrotoluene from nitrotoluene acidic wastewater as claimed in claim 1, wherein: the delivery pump is a centrifugal pump.
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| CN110160986A (en) * | 2019-06-27 | 2019-08-23 | 湖北东方化工有限公司 | The rapid assay methods of spent acid density in a kind of TNT production |
| CN111603869A (en) * | 2020-06-04 | 2020-09-01 | 湖北东方化工有限公司 | Novel polynitrotoluene dust collection process |
| CN113371768B (en) * | 2021-05-31 | 2023-04-18 | 湖北东方化工有限公司 | TNT waste acid-residual liquid recovery process and device |
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