CN110229046B - Device and method for extracting glycerol and glycerol-like alcohol from epoxy wastewater evaporation mother liquor - Google Patents
Device and method for extracting glycerol and glycerol-like alcohol from epoxy wastewater evaporation mother liquor Download PDFInfo
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- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
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Abstract
The invention relates to a device and a method for extracting glycerol and glycerol-like alcohol from an epoxy wastewater evaporation mother solution. The extraction method comprises the following steps: (1) preheating; (2) rectifying; (3) sectional heat exchange; (4) post-treatment. According to the invention, industrial glycerin with the concentration of 95.5-99% is obtained through rectification and stepwise cooling of evaporation mother liquor (concentrated glycerin mother liquor), and the rectification residue is subjected to molecular distillation under the conditions of high vacuum and high temperature to produce the polymerized glycerin and polyethylene glycol PEG400.
Description
Technical Field
The invention relates to a device and a method for extracting glycerin and polyalcohol from an epoxy wastewater evaporation concentration mother solution, belonging to the technical field of epoxy resin production.
Background
The total cost of liquid epoxy resin in the market of China and 2016 is 131.5 ten thousand tons, wherein the import of the liquid epoxy resin is 23.50; 200 ten thousand tons of epoxy wastewater produced by the annual production of the epoxy resin factories in 2016 years, wherein the average COD concentration of the wastewater is 9000-18000PPM, the salt content is 20-24%, the glycerol concentration is about 1-1.5%, and other organic matters are 0.2-0.4% (aged resin, triethyl benzyl amine chloride or glycol polyoxyethylene ether, phenol glycidyl ether and the like). The concentration of organic matters in the existing epoxy concentration mother solution is more than or equal to 40%, and the main treatment modes are as follows:
(1) The incineration treatment of organic waste liquid is the most common treatment method, but because the concentrated mother liquor contains 10-15% of NaCl, halogenated compounds can be generated to corrode equipment during the incineration treatment of the waste liquid, and simultaneously, the NaCl is easy to block the channel of the incinerator, so that the design requirement on the incinerator is higher.
(2) Concentrating the mother liquor until the organic matter content is more than or equal to 80%, and then incinerating: the 40% concentrated mother liquor is further concentrated into mother liquor: the organic matter content is more than or equal to 80 percent (the main components are 60-65 percent of glycerin, 10-15 percent of polyglycerol, about 7 percent of water, the NaCL content is less than or equal to 4 percent, the NaCl content is less than or equal to 5 percent of other organic matters (benzyl amine chloride, polyethylene glycol 400, polypropylene and the like), the mother liquor is concentrated and then enters an incinerator for incineration treatment, and the tail gas is discharged after alkali spray absorption.
(3) After desalting, mixing and diluting the concentrated mother solution with other waste water with low COD, and then carrying out catalytic oxidation and biochemical treatment: after desalting 40% concentrated mother liquor, mixing with other wastewater to dilute organic matters, carrying out catalytic oxidation and biochemical treatment, discharging the treated organic matters into an urban sewage comprehensive treatment tank for further treatment, and discharging the treated organic matters.
The three processing methods have the defects of high processing cost, high difficulty and great resource waste.
(4) The Chinese patent application No. 201710164554.9 discloses an epoxy resin high-salt wastewater treatment system, which comprises a high-salt wastewater pretreatment system, an MVR system, a secondary industrial refined salt preparation system and a glycerol preparation system, and can completely recycle glycerol in the epoxy resin high-salt wastewater.
However, the method can only be used for theoretical deduction and laboratory experiments, and industrial mass production cannot be realized basically. The MVR heat pump technology is adopted to evaporate the epoxy wastewater, when the concentration of high-boiling-point organic matters in an evaporation system is more than or equal to 20%, the epoxy wastewater concentrated mother liquor is discharged from the MVR evaporation system for additional treatment, otherwise, the temperature of the MVR evaporation system is increased, a compressor cannot suck steam to start surge, and the normal start-up of the MVR heat pump system is affected; if the concentrated mother solution with the concentration is fed into a thin film evaporation system, because the mother solution contains a large amount of moisture, the moisture in the thin film evaporation system is changed into water vapor preferentially, and under the high vacuum condition, the working temperature of the thin film evaporator is 120 ℃ only can obtain the evaporation condensate with the concentration of glycerin less than or equal to 10%, and 95% of glycerin cannot be obtained (which is verified by an industrial pilot plant in a laboratory).
The MVR heat pump evaporation concentration mother liquor material is a mixture of NaCl, water, polymerized glycerol, N, N-dimethylamide, N-Jier ethylamine, polyether substances, phenol glycidol and the like, when the mother liquor component is complicated and enters a thin film evaporation system for evaporation, water is flashed, nano salt is generated in an organic phase by salt, and a paste formed by the nano salt, the glycerol and other organic matters is left in a heavy component, so that the subsequent treatment is difficult and can only become dangerous waste.
The main components of the epoxy wastewater concentration mother solution are as follows: glycerin, water, polymerized glycerin, N, N-dimethylamide, N-Jier ethylamine and polyether substances, wherein the glycerin, the water, the polymerized glycerin, the N, N-dimethylamide, the N-Jier ethylamine and the polyether substances are azeotropic systems and cannot obtain pure glycerin by a simple thin film evaporation process when the glycerin, the water, the polymerized glycerin, the N-dimethylamide, the N-Jier ethylamine and the polyether substances are evaporated by the thin film evaporation process; the obtained mixture of glycerin, amine, ether and water (such as low concentration of glycerin in concentrated mother liquor, as long as the water content is more than 10%, evaporation at the temperature of less than or equal to 150 ℃ under high vacuum condition, and glycerin cannot be obtained in film evaporation); in addition, under the vacuum condition, the heavy component obtained by evaporation can only become dangerous waste due to the higher salt content, and 95% of glycerin can not be obtained from the light component. The patent has no practical significance only by theory, and has no industrial mass production popularization value.
(5) The Chinese patent application No. 20110373337.3 discloses a method for treating salt-containing glycerol wastewater, which comprises the steps of adding n-butanol which is 1.3-3.3 times of the total amount of the salt-containing wastewater, heating for desalting, recovering the n-butanol, dehydrating to obtain 99.9% of glycerol, wherein organic components in the epoxy wastewater are relatively complex, the use treatment cost in the epoxy wastewater is high by using an n-butanol extraction process, the glycerol content in the epoxy wastewater is only about 1%, the salt content is 24%, the other organic matters are 0.5-0.8%, and the wastewater volume per ton of the product is about 1.8 tons. If the method is used for treatment, the material consumption and energy consumption cost are high, the generated salt contains n-butyl alcohol, glycerol and other organic matters, the generated salt can only be used as dangerous waste for treatment, the waste water treatment cost is high, the process is extremely unstable, the generated salt can only be used as a research result of a laboratory, and the process is verified in the laboratory to be unsuitable for epoxy waste water, so that the process is not possible to realize industrial mass production.
(6) The Chinese patent publication No. CN 1073373087A discloses a device and a process for extracting glycerol from epoxy resin high-salt wastewater concentrate; it adopts first-stage forced evaporation and second-stage film evaporation to concentrate glycerine to 80-85%, and makes centrifugal separation, then makes third-stage film evaporation to concentrate glycerine to 95%, and according to the technological condition provided by said method it is characterized by that it is not capable of obtaining 95% of industrial glycerine, (1) the evaporation pressure of three-stage film evaporation system described in said claim is controlled to-0.07-0.095 MPa, and its temperature is controlled to 160-200 deg.C, at which it is impossible to evaporate glycerine, because under the pressure condition the glycerine boiling point of saturated salt glycerine solution is > 200 deg.C, and in addition glycerine is extremely easy to polymerize at 204 deg.C. In the example of the patent specification, the three-stage thin film evaporation temperature is 190 ℃, the glycerin cannot be obtained at the top of the pressure of 10KPa, the boiling point of pure glycerin is more than or equal to 213 ℃ and the boiling point of glycerin of saturated salt glycerin solution is more than 215 ℃ under the evaporation pressure of 10 KPa; therefore, no glycerin was distilled out under this condition.
Disclosure of Invention
In order to solve the technical problems, the invention provides a device and a method for producing glycerol and polymerized glycerol by purifying an epoxy resin evaporation mother solution. According to the invention, industrial glycerin with the concentration of 95.5-99% is obtained through rectification and stepwise cooling of evaporation mother liquor (concentrated glycerin mother liquor), and the rectification residue is subjected to molecular distillation under the conditions of high vacuum and high temperature to produce the polymerized glycerin and polyethylene glycol PEG400.
The invention is realized by adopting the following technical scheme.
A method for extracting glycerin and glycerol-like alcohol from an epoxy wastewater evaporation mother solution comprises the following steps:
(1) Preheating
Firstly, preheating an epoxy wastewater evaporation mother solution;
(2) Rectifying
Adopting a steam vacuum distillation mode to enable glycerin and water in the epoxy wastewater evaporation mother liquor to form an azeotrope;
(3) Sectional heat exchange and post-treatment
The glycerin in the obtained azeotrope is changed into liquid after primary heat exchange and secondary heat exchange, and then is cooled down to obtain glycerin with the purity of more than 95.5%; the obtained glycerin with the purity of more than 95.5 percent is further subjected to vacuum deodorization and active carbon decolorization to obtain industrial glycerin;
(4) Extraction of glycerol-like alcohols
Concentrating the rectification residual liquid in the step (2) further, separating and desalting; washing and refining the obtained salt to obtain industrial salt; and the residual liquid after desalting is separated into glycerin, polymerized glycerin and PEG400 by adopting a molecular short-range distillation mode.
The following details the steps:
in the step (1), the epoxy wastewater evaporation mother liquor is glycerin concentration mother liquor with the organic matter concentration of more than or equal to 78% obtained by performing MVR evaporation concentration and single-effect evaporation concentration on the epoxy wastewater to obtain desalination mother liquor or performing film evaporation concentration on the desalination mother liquor.
In the step (1), the temperature of the epoxy wastewater evaporation mother liquor reaches 90-130 ℃ after preheating.
In the step (2), the rectification conditions are as follows: vacuum degree is less than or equal to 5KPa, temperature is 130-195 ℃, and open dry steam stripping is adopted.
In the step (3), the sectional heat exchange comprises three-stage heat exchange; the primary heat exchange adopts the epoxy wastewater evaporation mother liquor as a heat exchange medium, and the temperature of the primary heat exchange is 115-130 ℃ and the pressure is less than or equal to 5KPa.
The secondary heat exchange adopts air heat exchange or water heat exchange, the temperature of the secondary heat exchange is 90-120 ℃, and the pressure is less than or equal to 5KPa.
In the process, the glycerin in the azeotrope is changed into liquid after primary heat exchange and secondary heat exchange, and then is cooled down to obtain glycerin with purity of more than 95.5%; and water and other low-boiling-point substances still move forward to the third-stage heat exchange for cooling in a gas form after the second-stage heat exchange, so that glycerin sweet water with the glycerin concentration of 15-45% is obtained.
The three-stage heat exchange adopts circulating water condensation, the temperature of the three-stage heat exchange is less than or equal to 32 ℃, and the pressure is less than or equal to 5KPa; the non-condensable gas which is not completely cooled is further condensed by cold well chilled water, the condensing temperature is 5 ℃, and the pressure is less than or equal to 5kPa.
In the step (3), the glycerin and sweet water is subjected to single-effect evaporation concentration to obtain concentrated solution with glycerin content more than or equal to 65%, and then the concentrated solution is used as the epoxy evaporation concentration mother solution for continuous use.
The invention also provides a device for extracting glycerol and glycerol-like alcohol from the epoxy wastewater evaporation mother liquor, which comprises: the device comprises a rectification system, a glycerol purification and separation unit, a heat exchange unit, a salt centrifugation and recrystallization unit, a material conveying unit, a vacuum system and an automatic control programming control system;
wherein, the rectification system includes: an epoxy wastewater evaporation concentration mother liquor storage tank, a first heat exchanger, a preheater and a distillation kettle;
the glycerol purification and separation unit comprises: foam separator, donor, mao Ganyou storage tank, decolorizing kettle, filter press, and glycerol product tank;
the heat exchange unit includes: a preheater, a first heat exchanger, a second heat exchanger, and a third heat exchanger;
the centrifugation and recrystallization unit of the salt comprises: a salt tank and a salt slurry storage tank;
the connection relation among the devices is as follows:
the outlet of the epoxy wastewater evaporation concentration mother liquor tank is connected with a condensing medium inlet pipeline of the first heat exchanger; the condensing medium outlet of the first heat exchanger is connected with an inlet pipeline of a preheating tank, the outlet of the preheating tank is connected with a material inlet pipeline of an evaporation kettle, the lower outlet of the evaporation kettle is connected with an upper inlet pipeline of a salt box, the lower outlet of the salt box is connected with a liquid return first inlet pipeline of the evaporator, the other lower outlet of the salt box is connected with an upper feed inlet pipeline of a salt slurry storage tank, the liquid outlet of the salt slurry storage tank is connected with a molecular short-path distillation storage tank of the next procedure through a pipeline, and the lower outlet of the salt slurry storage tank is connected with a centrifuge through a pipeline;
the vapor phase outlet of the distillation still is connected with the inlet of a foam separator, the liquid phase outlet (lower outlet) of the foam separator is connected with the second return port of the distillation still, the vapor phase outlet of the foam separator is connected with the vapor phase inlet of a first heat exchanger, the vapor phase outlet of the first heat exchanger is connected with the vapor phase inlet of a second heat exchanger through a pipeline, the liquid phase outlet of the first heat exchanger is connected with the inlet of a first capillary glycerol donor, and the lower liquid outlet of the first capillary glycerol donor is connected with the feed inlet of a Mao Ganyou storage tank through a pipeline; the gas phase outlet of the first heat exchanger is connected with the inlet of the second heat exchanger through a vacuum pipeline, the liquid phase outlet is connected with the inlet of the second capillary glycerol donor, and the lower liquid outlets of the first capillary glycerol donor and the second capillary glycerol donor are connected with the feed inlet of the Mao Ganyou storage tank through pipelines; the gas phase outlet of the second heat exchanger is connected with the vacuum pipeline and is connected with the inlet of the third heat exchanger, the liquid phase outlet of the third heat exchanger is connected with the glycerol rectification sweet water tank through the pipeline, the gas phase outlet of the third heat exchanger is connected with the inlet of the cold well in front of the vacuum pump, and the quasi-well gas phase outlet is connected with the vacuum pump;
the lower outlet of the Mao Ganyou storage tank is connected with the inlet of a Mao Ganyou material conveying pump, the outlet pipeline of the glycerol conveying pump is connected with the inlet pipeline of a Mao Ganyou decoloring and deodorizing kettle, the lower outlet of the decoloring and deodorizing kettle is connected with the inlet of a glycerol filter press, the outlet of the glycerol filter press is connected with the inlet of a glycerol finished product storage tank, and the outlet packaging system of the glycerol finished product storage tank is connected through a pipeline.
The specific working principle of the device for extracting glycerol and glycerol-like alcohol from the epoxy wastewater evaporation mother liquor is as follows:
(1) Preheating: the epoxy wastewater evaporation mother liquor is treated by a rectification system and then enters an epoxy wastewater evaporation concentration mother liquor storage tank 1, is sucked in vacuum or conveyed by a pump, and the inlet amount of crude glycerine is regulated by a flowmeter, and enters a preheater 2 to be preheated to 120 ℃ after being preheated to 90 ℃ by a first heat exchanger 3;
(2) And (3) rectifying: the preheated epoxy wastewater evaporation mother liquor enters a distillation kettle 4 for distillation to obtain an azeotrope of glycerol and water;
(3) And (3) sectional heat exchange: removing foam from the azeotrope through a foam separator 5, and refluxing condensate to a distillation kettle; the glycerine water azeotrope continuously passes through the first heat exchanger 3, the second heat exchanger 6 and the third heat exchanger 7 to condense glycerine with different concentrations, and is respectively collected in the glycerine feed device 9, the glycerine feed device 10 and the glycerine feed device 11, when distillation is started, the valves of the first heat exchanger 3, the second heat exchanger 6, the glycerine feed device 9 and the glycerine feed device 10 are firstly closed, the valves of the vapor phase pipeline to the glycerine feed device 8 are opened, if the concentration of the condensed glycerine is less than 95%, the distilled water is required to be distilled again by the distillation kettle 4, after the concentration of the glycerine reaches 96.5%, the valves of the first heat exchanger 3 to the glycerine feed device 9 are opened, the glycerine with the concentration greater than 96.5% is conveyed to the glycerine feed device 9, the valves of the second heat exchanger 6, the glycerine with the concentration greater than 95% are sequentially opened, the glycerine is conveyed to the glycerine feed device 10, and after the concentration reaches the specified liquid level, the glycerine enters the Mao Ganyou storage tank 12; the non-condensable gas condensed by the first heat exchanger 3 and the second heat exchanger 6 enters the condensed liquid in the third heat exchanger 7 and enters the evaporator 11, and as the concentration of glycerin in the material in the evaporator 11 is lower than 95.5 percent, and the N, N-dimethylamide is contained, the normal pressure boiling point is lower than 160 ℃ and the low volatile matters (nitrogen-containing organic matters and polyethers float on the surface), the lower layer returns the glycerin aqueous solution to the epoxy wastewater evaporation concentration mother liquor storage tank 1 for distillation again or goes to the single-effect evaporation mother liquor tank, and the upper layer organic impurities are separated and removed from the system.
Post-treatment: the distilled glycerin collected in the teaching device 9 and the teaching device 10 is put into a raw glycerin storage tank 12, is pumped into a decoloring kettle 14 through a material conveying pump 13 for decoloring and deodorizing treatment, and is filtered through a filter press 15 to obtain the finished glycerin (the glycerin can also be filtered and decolored by adopting fixed granular carbon and purified by a deodorizing bed), and the glycerin which is treated to reach the market standard enters a glycerin finished product tank 16 for waiting for packaging glycerin finished products.
(4) Extraction of glycerol-like alcohol: along with the continuous distillation of the glycerol, salt in the crude glycerol in the distillation kettle 4 is successively deposited in a salt box 17 under the distillation kettle, after two thirds of salt slurry in the salt box 17 is filled, the salt slurry in the salt box 17 is conveyed into a salt slurry storage tank 18 by steam, after centrifugal desalination, the filtrate is subjected to short-range molecular distillation to separate out the glycerol, the polyglycerol and the PEG400, the PEG400 and the polyglycerol are recycled to an epoxy production device for recycling, and the glycerol is removed from the crude glycerol storage tank; and the salt separated by centrifugation is washed twice with saturated brine and then recrystallized and centrifugally separated to produce industrial salt.
Compared with the prior art, the invention has the following advantages:
(1) The method can ensure that the concentrated mother liquor does not need incineration treatment (the treatment cost of ton mother liquor is more than or equal to 7000 yuan/ton) or dilution biochemical treatment, greatly reduces the treatment cost of the waste water of enterprises, and simultaneously greatly reduces the total discharge capacity of the waste water of the enterprises.
(2) The invention evaporates glycerin and water to form azeotrope by rectification, and is cooled by stages at the temperature 20 ℃ higher than the saturated vapor pressure of water and N, N-dimethyl amide, (the first stage adopts glycerin evaporation mother liquor heat exchange temperature is 115-130 ℃ and the pressure is less than or equal to 5KPa, the second stage adopts air condensation, the heat exchange temperature is 90-120 ℃ and the pressure is less than or equal to 5KPa, glycerin becomes liquid, the glycerin is fed into a glycerin feeding device, water and N, N-dimethyl amide enter into the third stage in vapor form to become water, the water enters into a sweet water tank, the non-condensate is cooled to below 15 ℃ by a cold well), the first stage and the second stage heat exchangers are condensed, the condensate is obtained Mao Ganyou with the glycerin concentration more than or equal to 95.5, the third stage heat exchange medium adopts water condensation, and the sweet water with the glycerin concentration more than or equal to 10% is obtained after being concentrated in the single-effect evaporation mother liquor tank, and is rectified again to obtain glycerin.
(3) Obtaining salt from the rectification residual liquid through centrifugal separation, producing industrial salt after washing and recrystallizing the salt with saturated epoxy refining wastewater, and removing polymerized glycerol and PEG400 residues after the salt in the rectification residual liquid, wherein the polymerized glycerol and PEG400 residues can be recycled by adopting molecular distillation;
(4) Mother liquor after the residue is desalted is respectively recovered through molecular short-path distillation; PGE400 is reused as an epoxy catalyst for epoxy production, and polymerized glycerol is sold as a dispersing agent or used as a glycerol catalyst; the process has higher economic benefit and social benefit.
Drawings
FIG. 1 is a flow chart of the process for distilling glycerin from the epoxy wastewater concentrated mother liquor.
FIG. 2 is a flow chart of the process for rectifying glycerol from the concentrated mother liquor of the epoxy wastewater;
wherein: an epoxy wastewater evaporation concentration mother liquor storage tank (crude glycerol tank) 1, a preheater 2, a first heat exchanger 3, a distillation kettle 4, a foam separator 5, a second heat exchanger 6, a third heat exchanger 7, a fourth capillary glycerol provider 8, a first capillary glycerol provider 9, a second capillary glycerol provider 10, a third capillary glycerol provider 11, a Mao Ganyou storage tank 12, a pump 13, a decoloring kettle 14, a filter press 15, a glycerol finished product tank 16, a salt tank 17, a salt slurry storage tank 18 and a pump 19.
Fig. 3 is a structural diagram of an epoxy rectifying still.
Detailed Description
An example of industrial glycerin production by rectifying the concentrated mother liquor of the epoxy wastewater is described in detail below. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that several modifications and improvements can be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the invention.
The invention mainly aims at the concentrated mother liquor of epoxy wastewater (the concentration of organic matters in the mother liquor is more than or equal to 78 percent), industrial glycerin is produced by rectification, and the main components of the concentrated mother liquor are shown in tables 1 and 2.
TABLE 1 composition of concentrated mother liquor of wastewater with benzyl triethyl amine chloride as catalyst in epoxy resin production
| Sequence number | Substance name | Mass percent (%) | Category(s) |
| 1 | N, N-dimethylamide | 5.5-8.9 | Organic matter |
| 2 | N-benzyl diethylamine | 1.2-3.23 | Organic matter |
| 3 | Glycerol | 55-68.4 | Organic matter |
| 4 | Dimeric glycerol | 3.2-7.18 | Organic matter |
| 5 | Triglycerol | 1.6-6.5 | Organic matter |
| 6 | Tetrameric and above glycerins | 1-2.2 | Organic matter |
| 7 | NaCL | ≤5 | Inorganic salt |
| 8 | Water and its preparation method | ≤4.98 | / |
| 9 | Alkali | ≤1.0 | Inorganic salt |
TABLE 2 concentration of wastewater Using PEG400 or Ether obtained by polyol polycondensation as catalyst in epoxy resin production
Composition table of mother liquor
| Sequence number | Substance name | Mass percent | Category(s) |
| 1 | Glycerol | 55-68.4 | Organic matter |
| 2 | Polyglycerol | 1.1-12.14 | Organic matter |
| 3 | Polyethylene glycol-400 | 6.0-16 | Organic matter |
| 4 | NaCL | ≤6 | Inorganic salt |
| 5 | Water and its preparation method | ≤8.0 | / |
| 6 | Alkali | ≤1.0 | Inorganic salt |
Example 1A device for extracting glycerol and glycerol-like alcohol from an epoxy wastewater Evaporation mother liquor
The embodiment provides a device for extracting glycerol and glycerol-like alcohol from an epoxy wastewater evaporation mother solution, which comprises: the device comprises a rectification system, a glycerol purification and separation unit, a heat exchange unit, a salt centrifugation and recrystallization unit, a material conveying unit, a vacuum system and an automatic control programming control system;
wherein, the rectification system includes: an epoxy wastewater evaporation concentration mother liquor storage tank, a first heat exchanger, a preheater and a distillation kettle;
the glycerol purification and separation unit comprises: foam separator, donor, mao Ganyou storage tank, decolorizing kettle, filter press, and glycerol product tank;
the heat exchange unit includes: a preheater, a first heat exchanger, a second heat exchanger, and a third heat exchanger;
the centrifugation and recrystallization unit of the salt comprises: a salt tank and a salt slurry storage tank;
the connection relation among the devices is as follows:
the outlet of the epoxy wastewater evaporation concentration mother liquor tank is connected with a condensing medium inlet pipeline of the first heat exchanger; the condensing medium outlet of the first heat exchanger is connected with an inlet pipeline of a preheating tank, the outlet of the preheating tank is connected with a material inlet pipeline of an evaporation kettle, the lower outlet of the evaporation kettle is connected with an upper inlet pipeline of a salt box, the lower outlet of the salt box is connected with a liquid return first inlet pipeline of the evaporator, the other lower outlet of the salt box is connected with an upper feed inlet pipeline of a salt slurry storage tank, the liquid outlet of the salt slurry storage tank is connected with a molecular short-path distillation storage tank of the next procedure through a pipeline, and the lower outlet of the salt slurry storage tank is connected with a centrifuge through a pipeline;
the vapor phase outlet of the distillation still is connected with the inlet of a foam separator, the liquid phase outlet (lower outlet) of the foam separator is connected with the second return port of the distillation still, the vapor phase outlet of the foam separator is connected with the vapor phase inlet of a first heat exchanger, the vapor phase outlet of the first heat exchanger is connected with the vapor phase inlet of a second heat exchanger through a pipeline, the liquid phase outlet of the first heat exchanger is connected with the inlet of a first capillary glycerol donor, and the lower liquid outlet of the first capillary glycerol donor is connected with the feed inlet of a Mao Ganyou storage tank through a pipeline; the gas phase outlet of the first heat exchanger is connected with the inlet of the second heat exchanger through a vacuum pipeline, the liquid phase outlet is connected with the inlet of the second capillary glycerol donor, and the lower liquid outlets of the first capillary glycerol donor and the second capillary glycerol donor are connected with the feed inlet of the Mao Ganyou storage tank through pipelines; the gas phase outlet of the second heat exchanger is connected with the vacuum pipeline and is connected with the inlet of the third heat exchanger, the liquid phase outlet of the third heat exchanger is connected with the glycerin rectification sweet water tank and the crude glycerin storage tank through pipelines, the gas phase outlet of the third heat exchanger is connected with the inlet of the cold well in front of the vacuum pump, and the quasi-well gas phase outlet is connected with the vacuum pump;
the lower outlet of the Mao Ganyou storage tank is connected with the inlet of a Mao Ganyou material conveying pump, the outlet pipeline of the glycerol conveying pump is connected with the inlet pipeline of a Mao Ganyou decoloring and deodorizing kettle, the lower outlet of the decoloring and deodorizing kettle is connected with the inlet of a glycerol filter press, the outlet of the glycerol filter press is connected with the inlet of a glycerol finished product storage tank, and the outlet packaging system of the glycerol finished product storage tank is connected through a pipeline.
Example 2 method for producing Industrial Glycerol by rectifying concentrated mother liquor of epoxy wastewater
The embodiment provides a method for preparing industrial glycerin from epoxy wastewater concentrated mother liquor, which comprises the following steps:
(1) Preheating
The filtered epoxy wastewater evaporation concentration mother liquor is stored in a storage tank 1, is conveyed to a first heat exchanger 3 through vacuum suction or a pump to be preheated to 90 ℃, then enters a preheater 2 to be preheated to 120 ℃, finally enters a distillation kettle 4, and the entering amount of crude glycerine is regulated through a flowmeter.
(2) Rectifying
Before the mother liquor of the epoxy wastewater evaporation concentration enters a kettle, a vacuum pump is started, continuous feeding is started after the pressure in the kettle reaches the rectification requirement condition (the vacuum degree is less than or equal to 5KPa and the temperature is 130-195 ℃), and distillation is performed through steam heating;
(3) Sectional heat exchange and post-treatment
Removing foam from the distilled glycerin and water azeotrope through a foam separator 5, refluxing condensate to a distillation kettle, sequentially passing through a first heat exchanger 3, a second heat exchanger 6 and a third heat exchanger 7, condensing to obtain glycerin with different concentrations, and respectively collecting the glycerin in corresponding heat exchangers 9, 10 and 11;
the specific operation is as follows: when distillation starts, the valves of the first heat exchanger 3 and the second heat exchanger 6 for feeding glycerol to the glycerol feeding devices 9 and 10 are firstly closed, the valves of the vapor phase pipelines for feeding the glycerol to the glycerol feeding devices 8 are opened, and the glycerol is required to be distilled back to the distillation kettle 4 for rectification again because the concentration of the initially condensed glycerol is less than 95 percent, and after the concentration of the glycerol reaches 95.5 percent, the valves of the first heat exchanger 3 and the second heat exchanger 6 for feeding the glycerol to the glycerol feeding devices 9 and 10 are opened, and the glycerol with the concentration of more than 95.5 percent is conveyed to the glycerol feeding devices 9 and 10, and after the glycerol reaches a specified liquid level, the glycerol enters a Mao Ganyou storage tank 12; the concentration of glycerin condensed from the third heat exchanger is lower than 95.5%, and the glycerin is returned to the crude glycerin storage tank 1 for distillation again after being received.
The first heat exchanger 3 uses the epoxy wastewater evaporation concentration mother liquor as a medium to exchange heat with the distillation mixed gas, the temperature of the glycerol mixed gas at the outlet is more than or equal to 120 ℃, and the second heat exchanger 6 uses air for condensation, and the temperature is more than or equal to 90 ℃; the non-condensable gas condensed by the first heat exchanger 3 and the second heat exchanger 6 enters the third heat exchanger 7 to be condensed, and the condensate enters the feeding device 11, because the glycerol concentration of the material in the feeding device 11 is lower than 95.5 percent, and the material contains N, N-dimethylamide and low volatile matters with the normal pressure boiling point lower than 160 ℃ (nitrogen-containing organic matters and polyethers can float on the surface), the lower layer is the glycerol aqueous solution, and the glycerol aqueous solution returns to the crude glycerol storage tank 1 to be distilled again or goes to the single-effect evaporation mother liquid tank to be concentrated again, and the upper layer organic impurities are separated and removed from the system; non-condensable gas which cannot be condensed by three-stage heat exchange enters a cold well in front of a vacuum pump, and the cold well temperature is less than or equal to 6 ℃ for further cooling and then enters a tail gas treatment system of a glycerol device for innocent treatment and then is emptied.
Post-treatment: the distilled glycerin collected in the receivers 9, 10 is put into a raw glycerin storage tank 12, pumped into a decoloring kettle (decoloring and deodorizing pot) 14 by a pump 13 for purifying treatment, heated and deodorized under absolute pressure, decolored by adding activated carbon, filtered by a filter press 15 to obtain the finished glycerin (glycerin purifying treatment can also be carried out by adopting a fixed granular carbon filtering decoloring and deodorizing bed), and the glycerin which reaches the commercial standard is processed to enter a glycerin finished product tank 16 for waiting for the quality data of the packaged glycerin finished product to be shown in Table 3.
TABLE 3 Table 3
(4) Extraction of glycerol-like alcohols
Along with the distillation, the distillation residues and salt in the distillation kettle are settled in a salt box 17 below the distillation kettle, when the salt slurry in the salt box reaches 2/3, the salt slurry is sent into a salt slurry storage tank 18 by steam, and after concentration for many times, the salt is removed by centrifugal separation, and the distillation residual liquid is separated and distilled for short-distance distillation to recover glycerin, polymerized glycerin and PEG400, and glycerin returns Mao Gan oil tank; PEG400 and polyglycerol mixture are used as catalyst for epoxy production.
The separated salt is washed by saturated epoxy refining wastewater, recrystallized for 2-3 times, and centrifugally separated to produce industrial wet salt, and the quality data of the industrial wet salt are shown in Table 4.
TABLE 4 Table 4
After the distillation still continuously works for 5-8 days, inorganic and organic impurities in the distillation still are gradually increased, so that the distillation efficiency is affected; to improve the distillation efficiency, after stopping the feed and continuing the distillation for 1-2 hours, the raffinate is sent under pressure to a salt slurry tank 18 for desalting and raffinate collection. And (5) adding water to clean the distillation kettle, and preparing before driving next time.
While the invention has been described in detail in the foregoing general description and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the invention and are intended to be within the scope of the invention as claimed.
Claims (7)
1. A method for extracting glycerin and glycerol-like alcohol from an epoxy wastewater evaporation mother solution, which is characterized by comprising the following steps:
(1) Preheating
Firstly, preheating an epoxy wastewater evaporation mother solution;
(2) Rectifying
Vacuum distillation is adopted to enable glycerin and water in the epoxy wastewater evaporation mother liquor to form an azeotrope; the rectification conditions are as follows: vacuum degree is less than or equal to 5kPa, temperature is 130-195 ℃, and open dry steam stripping is adopted;
(3) Sectional heat exchange and post-treatment
The glycerin in the obtained azeotrope is changed into liquid after primary heat exchange and secondary heat exchange, and then is cooled down to obtain glycerin with the purity of more than 95.5%; the obtained glycerin with the purity of more than 95.5 percent is further subjected to vacuum deodorization and active carbon decolorization to obtain industrial glycerin; the primary heat exchange adopts the epoxy wastewater evaporation mother liquor as a heat exchange medium, and the temperature of the primary heat exchange is 115-130 ℃ and the pressure is less than or equal to 5kPa; the secondary heat exchange adopts air heat exchange or water heat exchange, the temperature of the secondary heat exchange is 90-120 ℃, and the pressure is less than or equal to 5kPa;
(4) Extraction of glycerol-like alcohols
Concentrating the rectification residual liquid in the step (2) further, separating and desalting; washing and refining the obtained salt to obtain industrial salt; and the residual liquid after desalting is separated into glycerin, polymerized glycerin and PEG400 by adopting a molecular short-range distillation mode.
2. The method according to claim 1, wherein in the step (1), the epoxy wastewater evaporation mother liquor is glycerol concentration mother liquor with an organic matter concentration of not less than 78% obtained by performing MVR evaporation concentration, single-effect evaporation concentration desalination mother liquor or film evaporation concentration desalination mother liquor on the epoxy wastewater.
3. The method according to claim 1, wherein in the step (1), the temperature of the epoxy wastewater evaporation mother liquor reaches 90-130 ℃ after preheating.
4. A method according to any one of claims 1-3, characterized in that in step (3) water and other low boiling point substances are still moved forward in gaseous form after the secondary heat exchange to the tertiary heat exchange for cooling, resulting in glycerin sweet water with glycerin concentration of 15-45%.
5. The method of claim 4, wherein the three-stage heat exchange is performed by condensing circulating water, the temperature of the three-stage heat exchange is less than or equal to 32 ℃, the pressure is less than or equal to 5kPa, and non-condensable gases which are not completely cooled are further condensed by chilled water.
6. The method of claim 4, wherein the glycerin sweet water is concentrated by single-effect evaporation to obtain a concentrated solution with the glycerin content of more than or equal to 65%, and the concentrated solution is returned to the epoxy wastewater evaporation concentration mother solution for continuous use.
7. A device for extracting glycerin and glycerol-like alcohol from an epoxy wastewater evaporation mother liquor, comprising: the device comprises a rectification system, a glycerol purification and separation unit, a heat exchange unit, a salt centrifugation and recrystallization unit, a material conveying unit, a vacuum system and an automatic control programming control system;
wherein, the rectification system includes: an epoxy wastewater evaporation concentration mother liquor storage tank, a first heat exchanger, a preheater and a distillation kettle;
the glycerol purification and separation unit comprises: foam separator, donor, mao Ganyou storage tank, decolorizing kettle, filter press, and glycerol product tank;
the heat exchange unit includes: a preheater, a first heat exchanger, a second heat exchanger, and a third heat exchanger;
the centrifugation and recrystallization unit of the salt comprises: a salt tank and a salt slurry storage tank;
the connection relation among the devices is as follows:
the outlet of the epoxy wastewater evaporation concentration mother liquor tank is connected with a condensing medium inlet pipeline of the first heat exchanger; the condensing medium outlet of the first heat exchanger is connected with the inlet pipeline of the preheater, the outlet of the preheater is connected with the material inlet pipeline of the distillation still, the lower outlet of the distillation still is connected with the upper inlet pipeline of the salt box, the lower outlet of the salt box is connected with the liquid return first inlet pipeline of the evaporator, the other lower outlet of the salt box is connected with the upper feed inlet pipeline of the salt slurry storage tank, the liquid outlet of the salt slurry storage tank is connected with the molecular short-path distillation storage tank of the next procedure through a pipeline, and the lower outlet is connected with the centrifuge through a pipeline;
the vapor phase outlet of the distillation still is connected with the inlet of the foam separator, the liquid phase outlet of the foam separator is connected with the second return port of the distillation still, the vapor phase outlet of the foam separator is connected with the vapor phase inlet of the first heat exchanger, the vapor phase outlet of the first heat exchanger is connected with the vapor phase inlet of the second heat exchanger through a pipeline, the liquid phase outlet of the first heat exchanger is connected with the inlet of the first capillary glycerol donor, and the lower liquid outlet of the first capillary glycerol donor is connected with the feed inlet of the Mao Ganyou storage tank through a pipeline; the gas phase outlet of the first heat exchanger is connected with the inlet of the second heat exchanger through a vacuum pipeline, the liquid phase outlet is connected with the inlet of the second capillary glycerol donor, and the lower liquid outlets of the first capillary glycerol donor and the second capillary glycerol donor are connected with the feed inlet of the Mao Ganyou storage tank through pipelines; the gas phase outlet of the second heat exchanger is connected with the vacuum pipeline and is connected with the inlet of the third heat exchanger, the liquid phase outlet of the third heat exchanger is connected with the glycerol rectification sweet water tank through the pipeline, the gas phase outlet of the third heat exchanger is connected with the inlet of the cold well in front of the vacuum pump, and the gas phase outlet of the cold well is connected with the vacuum pump;
the lower outlet of the Mao Ganyou storage tank is connected with the inlet of a Mao Ganyou material conveying pump, the pipeline of the glycerol conveying pump outlet is connected with the inlet pipeline of a Mao Ganyou decoloring and deodorizing kettle, the lower outlet of the decoloring and deodorizing kettle is connected with the inlet of a glycerol filter press, the outlet of the glycerol filter press is connected with the inlet of a glycerol finished product storage tank, and the outlet packaging system of the glycerol finished product storage tank is connected through a pipeline;
the rectification conditions of the distillation kettle are as follows: vacuum degree is less than or equal to 5kPa, temperature is 130-195 ℃, and open dry steam stripping is adopted.
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