CN117843433A - Method for purifying and recovering dimethylbenzene and ethanol in multiphase mixed waste liquid - Google Patents
Method for purifying and recovering dimethylbenzene and ethanol in multiphase mixed waste liquid Download PDFInfo
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Abstract
The invention discloses a method for purifying and recovering dimethylbenzene and ethanol in multiphase mixed waste liquid, which comprises the steps of carrying out gradient heating and reduced pressure distillation on multiphase mixed waste liquid, mixing distillate with an extractant, standing and layering; taking the layered lower layer material liquid to carry out hypergravity rectification to obtain an upper layer rectification liquid, namely the purified ethanol; taking layered upper layer feed liquid, washing, standing and layering to obtain purified dimethylbenzene; according to the purification and recovery method disclosed by the invention, under the condition of not consuming a large amount of heat energy, the xylene and the ethanol in the multiphase mixed waste liquid are purified and recycled by combining reduced pressure gradient distillation with hypergravity rectification, the process flow is simple to operate, the energy consumption is low, the efficiency is high, the purification and reutilization of the organic solvent in the waste liquid in an intermittent production mode is realized, and the method is environment-friendly and the cost is saved.
Description
Technical Field
The invention relates to a purification and recovery method, in particular to a purification and recovery method for dimethylbenzene and ethanol in multiphase mixed waste liquid.
Background
Xylene belongs to aromatic hydrocarbon compounds, has a boiling point of 137-140 ℃ at normal temperature and normal pressure, is colorless liquid at normal temperature, and has special fragrance. Xylene is widely used as a solvent and a reaction medium in the chemical industry, can be used as a solvent for dissolving paint, coating, resin, adhesive and the like, and serves as a reaction medium in the chemical reaction process, thus being an important raw material for organic chemical industry. Ethanol has a boiling point of 78.4 ℃ at normal temperature and normal pressure, is a colorless transparent liquid which is easy to volatilize, has low toxicity, can be mutually dissolved with water in any ratio, has wine fragrance and slight irritation, and can be mixed with most organic solvents. Although the boiling points of the dimethylbenzene and the ethanol are very different at normal temperature, the dimethylbenzene and the ethanol are easy to form an azeotropic system, and the common rectification mode cannot obtain high-efficiency separation. In the industry, separation is realized by adopting an extraction and rectification mode, but the waste liquid system also contains an emulsifying agent, so that the extraction process is greatly influenced, and besides, the traditional rectification extraction tower has larger occupied area and higher cost, and is not suitable for small batch intermittent waste liquid treatment. Therefore, a separation method with simple process operation, low cost and high efficiency is urgently needed, and the purity of the recovered solvent is improved.
Patent CN101306982B discloses a method for intermittently extracting and rectifying ethanol/xylene, which uses p-diethylbenzene as an extractant to interact with xylene, and intermittently recovers distillate by controlling the temperature at the top of a rectifying tower, but the method does not propose a treatment method of ethanol/xylene transition distillate and the extractant p-diethylbenzene and xylene transition distillate, so that the recovery rate is greatly affected; furthermore, if the concentration of the waste liquid component changes and the proportion of the ternary system component in the treatment process changes, the temperature corresponding to the replacement of the collection tank is affected, and the purity of the collection liquid is caused to fluctuate. Patent CN105906471B discloses a method for separating xylene-ethylene glycol mixture by continuous azeotropic distillation, which uses a traditional rectifying tower as a main body, uses pure water as an entrainer for distillation, and has the feeding position of the entrainer at a 1 st column plate, which is easy to cause instability and high operation difficulty; in addition, in the azeotropic distillation process, if the composition of the entrainer and the raw material is not proper, the separation effect is poor, and the purity and quality of the product are affected.
Disclosure of Invention
The invention aims to: the invention aims to provide a method for purifying and recycling dimethylbenzene and ethanol in multiphase mixed waste liquid, which has high efficiency and high purity of recycled solvent.
The technical scheme is as follows: the invention relates to a method for purifying and recovering dimethylbenzene and ethanol in multiphase mixed waste liquid, which comprises the following steps:
(1) The multiphase mixed waste liquid is distilled under reduced pressure and temperature gradient, the distillate is mixed with the extractant, and the mixture is stood for layering;
(2) Performing hypergravity rectification on the layered lower-layer feed liquid in the step (1) to obtain upper-layer rectification liquid, namely purified ethanol;
(3) And (3) taking the upper layer material liquid layered in the step (1), washing with water, standing and layering to obtain the purified dimethylbenzene.
Preferably, the multiphase mixed waste liquid contains ethanol, dimethylbenzene and a high molecular emulsifier.
Further, the polymer emulsifier is a cellulose derivative, and comprises cellulose esters: cellulose nitrate, cellulose acetate butyrate, cellulose xanthate and the like; cellulose ethers: methylcellulose, carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, cyanoethylcellulose, hydroxypropylcellulose, hydroxypropylmethyl cellulose and the like.
Preferably, in the step (1), the mass ratio of the multiphase mixed waste liquid to the extractant is 1:0.5 to 1.
Preferably, in the step (1), the extractant is 10 to 15 percentOr 10-15% NaCO 3 A solution.
Preferably, in step (1), stirring is performed during the distillation and mixing at a stirring speed of 50 to 80rpm.
Preferably, in the step (1), the distillation temperature is 30-45 ℃, and the gradient heating mode is to heat 3-5 ℃ every 1 h.
Preferably, in the step (1), standing and layering time is 2-4 hours.
Preferably, in the step (1), the pressure of the depressurization is-0.085 MPa to-0.095 MPa.
Preferably, in the step (2), the reflux ratio of the hypergravity rectification is 1:0.11-0.16.
Preferably, in the step (3), the washing times are 3 to 5 times, the standing time after each washing is 4 to 6 hours,
and discharging lower-layer wastewater, wherein the standing time after the last water washing is 40-48 h.
The principle of the invention: the invention adopts the modes of gradient heating, decompression distillation, extraction and hypergravity rectification to efficiently separate the dimethylbenzene and the ethanol in the multiphase mixed waste liquid; the method changes the disclosed mode of recycling and purifying the dimethylbenzene, combines reduced pressure distillation with hypergravity distillation under the condition of not consuming a large amount of heat energy through interaction of an extracting agent and the ethanol, purifies the dimethylbenzene and the ethanol in the multiphase mixed waste liquid for recycling, has simple operation of the process flow, low energy consumption and high efficiency, realizes the purification and recycling of the organic solvent in the waste liquid by an intermittent production mode, and is environment-friendly and cost-saving. In addition, unlike conventional separation systems, the mixed waste liquid contains an emulsifier, and the extraction and rectification type extractant which is currently mainstream is difficult to play a role. The invention removes the emulsifier by utilizing a gradient heating and decompression distillation mode, prevents the waste liquid bumping emulsifier from being accompanied, and ensures that the distillate of the ethanol/dimethylbenzene system is quickly mixed with the extractant to achieve the purpose of separation.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: (1) The purity of the recovered solvent is high, and the ethanol content in the waste liquid is 62.4-70.0 percent, the dimethylbenzene content is 23.2-28.4 percent, and the waste liquid is purified to 99.20 percent and more than 99.50 percent respectively; (2) The reaction is mild, compared with the conventional rectification process, the equipment floor area and the energy consumption in the production process are reduced, the method is suitable for industrial application, and the concentrated solution can be distilled under reduced pressure to obtain the crude product of the emulsifier, so that the possibility is provided for subsequent recovery and purification.
Drawings
FIG. 1 is a process flow diagram of the reduced pressure distillation and extraction steps of the present invention;
wherein, 1 is a distillation kettle, 2 is a collection kettle, 3 is a distillation kettle stirrer, 4 is a collection kettle stirrer, 5 is a condenser, and 6 is a vacuum air extractor;
FIG. 2 is a process flow diagram of the hypergravity rectification step of the present invention;
wherein 7 is a raw material tank, 8 is a reboiler, 9 is a rectifier, 10 is a main condenser, 11 is a tail condenser, 12 is a product condenser, 13 is an ethanol collecting tank, and 14 is a flow meter.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
Example 1
(1) As shown in fig. 1, 240.0kg of multiphase mixed waste liquid containing 63.5% xylene, 24.8% ethanol and 11.7% methylcellulose was added to a distillation still 1, 180.0kg of extractant was added to a collection still 2, the extractant was 10% NaCl solution, and a distillation still stirrer 3 and a collection still stirrer 4 were turned on at a rotation speed of 60rpm; opening a collecting kettle vacuum pumping valve 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.09 MPa; starting a condenser 5, heating a distillation kettle through a medium, lifting the temperature by 5 ℃ every 1h from 30 ℃, closing a collecting kettle stirrer until the distillation is finished at 45 ℃, and standing for 3h for layering;
(2) As shown in fig. 2, transferring the layered lower mixed material liquid in the step (1) to a raw material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; the reboiler 8 temperature was set at 85℃and the reflux ratio was set at 1:0.12. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid containing the extractant and a small amount of mixed solvent can be returned to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 42 hours, so as to obtain purified dimethylbenzene.
Example 2
The composition and rotational speed of the multiphase mixed waste liquid were changed as compared with example 1:
(1) 240.0kg of multiphase mixed waste liquid containing 66.4% of dimethylbenzene, 26.2% of ethanol and 7.4% of cellulose acetate is added into a distillation kettle 1, 180.0kg of extracting agent is mixed and added into a collecting kettle 2, the extracting agent is 10% of NaCl solution, and a distillation kettle stirrer 3 and a collecting kettle stirrer 4 are started at the rotating speed of 80rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.09 MPa; starting a condenser 5, heating a distillation kettle through a medium, lifting the temperature by 5 ℃ every 1h from 30 ℃, closing a collecting kettle stirrer until the distillation is finished at 45 ℃, and standing for 3h for layering;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; the reboiler 8 temperature was set at 85℃and the reflux ratio was set at 1:0.12. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 42 hours, so as to obtain purified dimethylbenzene.
Example 3
In comparison with example 2, the reduced pressure state of step (1) and the reflux ratio of step (2) were adjusted:
(1) 240.0kg of multiphase mixed waste liquid containing 66.4% of dimethylbenzene, 26.2% of ethanol and 7.4% of cellulose acetate is added into a distillation kettle 1, 180.0kg of extracting agent is mixed and added into a collecting kettle 2, the extracting agent is 10% of NaCl solution, and a distillation kettle stirrer 3 and a collecting kettle stirrer 4 are started at the rotating speed of 80rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.085 MPa; starting a condenser 5, heating a distillation kettle through a medium, lifting the temperature by 5 ℃ every 1h from 30 ℃, closing a collecting kettle stirrer until the distillation is finished at 45 ℃, and standing for 3h for layering;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; reboiler 8 temperature was set at 85 ℃, and reflux ratio was set at 1:0.16. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 42 hours, so as to obtain purified dimethylbenzene.
Example 4
Compared with example 2, the concentration of the extractant in step (1) and the reflux ratio in step (2) and the standing time in step (3) were adjusted:
(1) 240.0kg of multiphase mixed waste liquid containing 66.4% of dimethylbenzene, 26.2% of ethanol and 7.4% of cellulose acetate is added into a distillation kettle 1, 180.0kg of extracting agent is mixed and added into a collecting kettle 2, the extracting agent is 15% of NaCl solution, and a distillation kettle stirrer 3 and a collecting kettle stirrer 4 are started at the rotating speed of 80rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.09 MPa; starting a condenser 5, heating a distillation kettle from 30 ℃ through medium, lifting the temperature by 5 ℃ at intervals of 1h until the distillation at 45 ℃ is finished, closing a collecting kettle stirrer, and standing for 3h for layering;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; the reboiler 8 temperature was set at 85℃and the reflux ratio was set at 1:0.14. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 48 hours, so as to obtain purified dimethylbenzene.
Example 5
Compared with example 3, the extractant of step (1), the temperature of step (2) and the standing time of step (3) were adjusted:
(1) 240.0kg of multiphase mixed waste liquid containing 66.4% of dimethylbenzene, 26.2% of ethanol and 7.4% of cellulose acetate is added into a distillation still 1, 180.0kg of extracting agent is mixed and added into a collecting still 2, and the extracting agent is 10% of NaCO 3 Starting the solution, a distillation kettle stirrer 3 and a collection kettle stirrer 4, and rotating at 80rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.085 MPa; starting a condenser 5, heating a distillation kettle through a medium, lifting the temperature by 5 ℃ every 1h from 30 ℃, closing a collecting kettle stirrer until the distillation is finished at 45 ℃, and standing for 3h for layering;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; reboiler 8 temperature was set at 90 ℃, and reflux ratio was set at 1:0.16. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 48 hours, so as to obtain purified dimethylbenzene.
Comparative example 1
According to a method for separating a xylene-ethylene glycol mixture by continuous azeotropic distillation disclosed in patent CN105906471B, a multiphase mixed waste liquid containing 63.5% xylene, 24.8% ethanol and 11.7% methylcellulose is treated by azeotropic distillation. Pure water is used as an entrainer, and the feeding ratio of the entrainer to the raw material is 3:1, the azeotropic distillation tower plate number is 28, the dehydration tower plate number is 17, and the contents of the recovered dimethylbenzene and ethanol are shown in table 1.
Comparative example 2
Compared with example 1, the temperature raising method in step (1) was changed:
(1) 240.0kg of multiphase mixed waste liquid containing 63.5% of dimethylbenzene, 24.8% of ethanol and 11.7% of methyl cellulose is added into a distillation still 1, 180.0kg of extracting agent is added into a collecting still 2, the extracting agent is 10% of NaCl solution, and a distillation still stirrer 3 and a collecting still stirrer 4 are started at the rotating speed of 60rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.09 MPa; starting a condenser 5, heating a distillation kettle by a medium, rapidly heating to 45 ℃, maintaining distillation for 3 hours, and standing for 3 hours for layering after the distillation is finished;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; the reboiler 8 temperature was set at 85℃and the reflux ratio was set at 1:0.12. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 42 hours, so as to obtain purified dimethylbenzene.
Comparative example 3
The pressure state of step (1) was changed as compared to comparative example 2:
(1) 240.0kg of multiphase mixed waste liquid containing 63.5% of dimethylbenzene, 24.8% of ethanol and 11.7% of methyl cellulose is added into a distillation still 1, 180.0kg of extracting agent is added into a collecting still 2, the extracting agent is 10% of NaCl solution, and a distillation still stirrer 3 and a collecting still stirrer 4 are started at the rotating speed of 60rpm; starting a collecting kettle vacuum air extractor 6 to enable the vacuum gauge pressure indication number of the distilling kettle to be-0.06 MPa; starting a condenser 5, heating a distillation kettle by a medium, rapidly heating to 45 ℃, maintaining distillation for 3 hours, and standing for 3 hours for layering after the distillation is finished;
(2) Transferring the layered lower mixed material liquid obtained in the step (1) to a material tank 7 for performing hypergravity rectification, wherein the lower mixed material liquid mainly comprises ethanol, an extractant and a small amount of dimethylbenzene; the reboiler 8 temperature was set at 85℃and the reflux ratio was set at 1:0.12. Collecting the upper layer rectification liquid obtained after the hypergravity rectification to an ethanol collecting tank 13 to obtain purified ethanol; the lower layer rectification liquid can return to the step (1) for cyclic extraction, and the extractant is recovered;
(3) Taking the layered upper feed liquid in the step (1), wherein the upper feed liquid is mainly a crude product of dimethylbenzene, washing with pure water, standing, discharging lower wastewater, repeating for three times, wherein the standing time is 4 hours, and the last standing time is 42 hours, so as to obtain purified dimethylbenzene.
Performance tests of relevant indexes are carried out on the xylene and ethanol recovered in the examples 1-5 and the comparative examples 1-3, and the test items and test results are specifically shown in table 1.
Table 1, performance test data
As shown in table 1, in comparative example 1, ethanol and xylene cannot be separated efficiently by azeotropic distillation under the action of an emulsifier; by adopting the method, the dimethylbenzene and the ethanol with higher purity can be obtained, meanwhile, the crude product of the emulsifier can be obtained, the waste liquid is fully utilized to a great extent, and the recycling rate is improved. Meanwhile, the method has the advantages of less energy consumption and simple method, and is suitable for industrial application.
Compared with the embodiment 1, the comparative example 2 changes the gradient heating mode of reduced pressure distillation, and the violently boiling xylene/ethanol distillate can be accompanied with part of emulsifier to enter a collecting kettle, so that the process of the extractant is influenced, and the content of recovered xylene and ethanol is reduced; compared with comparative example 2, the working vacuum degree of reduced pressure distillation is reduced, on one hand, the boiling point of a mixed system is directly increased, the energy input is improved, and on the other hand, the distillation time is increased relative to comparative example 2, the efficiency of separation and purification is comprehensively reduced, and the purity of the recovered solvent is reduced.
Claims (10)
1. The method for purifying and recovering the dimethylbenzene and the ethanol in the multiphase mixed waste liquid is characterized by comprising the following steps of:
(1) The multiphase mixed waste liquid is distilled under reduced pressure and temperature gradient, the distillate is mixed with the extractant, and the mixture is stood for layering;
(2) Performing hypergravity rectification on the layered lower-layer feed liquid in the step (1) to obtain upper-layer rectification liquid, namely purified ethanol;
(3) And (3) taking the upper layer material liquid layered in the step (1), washing with water, standing and layering to obtain the purified dimethylbenzene.
2. The purification and recovery method according to claim 1, wherein the multiphase mixed waste liquid contains ethanol, xylene and a polymer emulsifier.
3. The purification and recovery method according to claim 1, wherein in the step (1), the mass ratio of the multiphase mixed waste liquid to the extractant is 1:0.5 to 1.
4. The method according to claim 1, wherein in the step (1), the extractant is 10 to 15% NaCl solution or 10 to 15% NaCO 3 A solution.
5. The purification and recovery method according to claim 1, wherein in the step (1), stirring is performed during the distillation and mixing at a stirring speed of 50 to 80rpm.
6. The purification and recovery method according to claim 1, wherein in the step (1), the distillation temperature is 30 to 45 ℃, and the gradient heating mode is to heat 3 to 5 ℃ every 1 hour.
7. The purification and recovery method according to claim 1, wherein in the step (1), the standing delamination time is 2 to 4 hours.
8. The purification and recovery method according to claim 1, wherein in the step (1), the pressure of the depressurization is-0.085 MPa to-0.095 MPa.
9. The purification and recovery method according to claim 1, wherein in the step (2), the reflux ratio of the hypergravity distillation is 1:0.11 to 0.16.
10. The purification and recovery method according to claim 1, wherein in the step (3), the number of times of washing is 3 to 5, the standing time after each washing is 4 to 6 hours, the lower layer waste water is discharged, and the standing time after the last washing is 40 to 48 hours.
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