CN111559819B - Method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater - Google Patents
Method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater Download PDFInfo
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Abstract
The invention discloses a method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater, which mainly comprises the following steps: carrying out evaporation concentration on the epoxidation alkaline washing wastewater, and recovering most of water, epoxypropane and azeotropic organic matters; crystallizing the concentrated wastewater to remove organic acid salt crystals; dehydrating and refining the obtained crude propylene glycol to obtain a propylene glycol product. The method is used for treating the propylene epoxidation alkali washing wastewater, and a medical-grade propylene glycol product can be produced; can recover most of propylene oxide, alcohol ketone, aromatic hydrocarbon and water in the wastewater; in addition, the treatment cost of the organic acid salt can be greatly reduced, the fuel quantity sent to the incinerator is reduced, and the energy consumption of the device is reduced. By adopting the method to treat the propylene epoxidation alkaline washing wastewater, 360-380 kg/h of propylene oxide can be recovered every ton of wastewater, the treatment cost of the wastewater is removed, and 190-270 yuan of economic benefit can be generated.
Description
Technical Field
The invention belongs to the field of chemical industry production wastewater treatment, and relates to a method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater.
Background
The hakon process is a process for producing propylene oxide by oxidizing propylene with hydrogen peroxide as an oxidizing agent, and many industrial propylene oxide production apparatuses such as a propylene oxide/styrene co-production apparatus, a propylene oxide/t-butyl alcohol (or methyl t-butyl ether) co-production apparatus, and a propylene oxide apparatus by the cumene process are currently available.
A typical co-oxidation propylene oxide production process includes at least the following steps:
(a) reacting organic matters (usually ethylbenzene, cumene, isobutane and the like) with oxygen in oxygen-containing gas to generate organic matter hydrogen peroxide;
(b) reacting organic hydrogen peroxide with propylene to produce propylene oxide and corresponding alcohol (such as methylbenzyl alcohol, dimethylbenzyl alcohol, and tert-butyl alcohol);
(c) the coproduced alcohols are dehydrated (or hydrogenolyzed) to form the corresponding olefins, such as styrene, alpha-methylstyrene, isobutylene.
Generally, the reaction step b is called epoxidation or co-oxidation, and organic hydrogen peroxide reacts with propylene to generate corresponding alcohol and propylene oxide, and at the same time, due to the strong oxidizing property of the organic hydrogen peroxide, the organic is also over-oxidized to generate some acidic substances, such as formic acid, benzoic acid, acetic acid, phenol, and the like. To prevent acid build-up in the recycle stream while avoiding the extensive use of corrosion resistant materials in subsequent processing steps, the epoxidation reaction stream is typically subjected to a caustic wash operation. NaOH or Na is often used industrially2CO3And (3) as a neutralizing agent, performing alkali washing on the epoxidation solution to remove acidic substances in the epoxidation solution.
While the alkaline washed epoxidation material will have some Na remained+Among the materials, they must be removed, otherwise the subsequent operations will cause problems of clogging of the equipmentThus, after the alkaline washing operation, a multistage washing operation is generally employed to remove Na from the epoxidized material+。
FIG. 1 shows a typical epoxidation caustic wash flowsheet.
Removing acidic substances in alkaline washing operation and removing Na in water washing operation+Meanwhile, the hydration of the propylene oxide can also occur, more propylene glycol is generated and enters into the water phase, and the loss of the propylene oxide material and the increase of the COD of the epoxidation alkaline washing wastewater are caused. Meanwhile, propylene oxide and aromatic alcohol (such as methylbenzyl alcohol and dimethylbenzyl alcohol) have certain solubility in a water phase, so that propylene glycol, propylene oxide, aromatic alcohol, organic acid salt, incompletely-reacted alkali and the like can be contained in the epoxidation alkali washing wastewater. The composition of this waste stream is typically: 90-95% of water, 0.8-1.5% of propylene oxide, 1.5-2.5% of propylene glycol, 0.1-0.5% of aromatic hydrocarbon (such as ethylbenzene and isopropylbenzene), 1-1.5% of alcohol ketone (methyl benzyl alcohol, dimethyl benzyl alcohol, tert-butyl alcohol and acetophenone), 0.1-0.2% of other low-boiling-point oxygen-containing compounds (such as methanol, formaldehyde, acetaldehyde, propionaldehyde and acetone), and 2-5% of organic acid salt and alkali. Generally, 0.5-0.8 ton of epoxidation alkaline washing wastewater is generated for each 1 ton of propylene oxide produced.
For the cyclo-oxidation wastewater, the current industrialized treatment methods mainly comprise two methods:
1. mixing the waste water with waste water generated by other units in the device, and treating by adopting a wet oxidation method and a suspension biochemical method;
2. mixed with waste water produced by other units in the device and then treated by adopting an incineration method.
All the wastewater in the device is mixed and then treated by the two methods, the wastewater properties of each unit are not separately treated, and a large amount of useful components in the epoxidation wastewater are not recycled, so that a large amount of high-added-value chemical raw materials are wasted, the properties of the mixed wastewater are more complex, and the treatment cost is higher. Researchers report that the cost for treating the wastewater produced by a 1-ton co-oxidation method propylene oxide device by adopting an incineration method is 500-600 yuan (Zhangxiong. high COD alkaline industrial wastewater treatment in propylene oxide production [ J ]. chemical engineering and equipment, 2019, (8): 296-298).
The waste water from the co-oxidation propylene oxide treatment device by wet oxidation and incineration is described in the literature "analysis of the generation and treatment status of waste water from propylene oxide production". (Wanglimei. propylene oxide production wastewater generation and treatment status analysis [ J ] Shandong chemical engineering, 2018,47(7):170-173, 177). In addition, Zhang Xiong introduced a method for treating propylene oxide wastewater by using a co-oxidation method in the "treatment of alkaline industrial wastewater with high COD in propylene oxide production" method, which can greatly reduce the treatment cost of wastewater, but still does not recover useful components in wastewater.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide a method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater, which can recover high value-added components such as propylene glycol, propylene oxide, aromatic hydrocarbons, alcohol ketones and the like in the wastewater.
The boiling points of main components in the epoxidation alkaline washing wastewater are sequenced, and the main components are epoxypropane, oxygen-containing organic substances, water, aromatic hydrocarbons, propylene glycol, alcohol ketone and salts.
Because the boiling point of the propylene oxide is low, the propylene oxide can be vaporized and discharged firstly, and the aromatic hydrocarbons and alcohol ketones (such as ethylbenzene, isopropylbenzene, methyl benzyl alcohol, dimethyl benzyl alcohol and acetophenone) with the boiling points higher than that of water can form minimum constant boiling substances with water, so that the aromatic hydrocarbons and the alcohol ketones can be removed from the wastewater by only heating the wastewater to evaporate a small amount.
Because propylene glycol has a higher boiling point than water and is completely miscible with water, it is necessary to completely evaporate the water in order to recover propylene glycol, which is also an industrial process for propylene glycol production.
Different from the industrial method for producing propylene glycol by hydrating propylene oxide, the epoxidation alkaline washing wastewater also contains a large amount of organic acid salt, so that the propylene glycol in the wastewater can be recovered by separating the propylene glycol from the organic acid salt.
According to the analysis, the invention provides a method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater, and the specific scheme flow is as follows:
1) and (3) carrying out evaporation concentration on the epoxidation alkali washing wastewater:
the epoxypropane, the aromatic hydrocarbon and the alcohol ketone are evaporated out together with water to form fresh water without salt, and the fresh water is returned to the step of washing the epoxidation material with water, so that the epoxypropane, the aromatic hydrocarbon, the alcohol ketone and the like in the wastewater can be recovered, most of the wastewater can be recovered, the water supplement amount of epoxidation washing operation is greatly reduced, and the water consumption is reduced;
because propylene oxide, aromatic hydrocarbon, alcohol ketone and water are evaporated, substances with boiling points higher than that of water, such as propylene glycol, organic acid salt and the like, are concentrated in an evaporation zone, the concentration multiple is generally set according to the concentration of the organic acid salt in a concentrated solution, and the operation requirement is that the concentration of the organic acid salt in the concentrated wastewater is kept at 10-50 wt%, and is preferably controlled at 20-30%;
in order to utilize low-grade heat, the triple-effect evaporator is preferably operated under a negative pressure condition, the operation pressure is generally controlled to be 10-500 kPaA, but at such a low pressure, propylene oxide is difficult to condense at normal temperature and can directly enter the vacuum pump, so that the consumption of the vacuum pump is increased, therefore, the preferred scheme is that the alkaline washing wastewater generated by propylene epoxidation is firstly subjected to normal-pressure flash evaporation, the propylene oxide in the wastewater is recovered and then is sent to the triple-effect evaporator for negative-pressure evaporation, and the consumption of the vacuum pump is greatly reduced.
Generally, the evaporation concentration equipment can adopt a single-stage evaporator, a multi-effect evaporator, a mechanical evaporator (MVR) and the like, preferably adopts the multi-effect evaporator and the mechanical evaporator, and the multi-effect evaporator generally preferably adopts 2-10-effect evaporation, so that the operation cost of the waste water evaporation concentration can be greatly reduced.
(2) And (4) feeding the concentrated wastewater into a flash evaporation crystallizer for crystallization, and separating out crystals.
The concentrated wastewater is heated and then sent into a flash evaporation crystallizer for crystallization. Most of the water and the propylene glycol are subjected to phase change and are converted into gas phase, and the content of the organic acid salt originally dissolved in the water phase exceeds the saturated solubility due to the evaporation of the solvent, so that crystals are precipitated and grow in a flash evaporator. The flash evaporation effluent, the propylene glycol and the possible carried organic acid salt enter a propylene glycol dehydration unit; the mother liquor containing the organic acid salt crystals is settled at the bottom of the crystallizer, the mother liquor containing only a small amount of fine crystals at the upper part is pumped out, and the mother liquor and the concentrated wastewater are boosted by a circulating pump, sent into a heater for heating and then sent into a flash evaporation crystallizer for continuous crystallization; the lower portion of the material containing larger crystal particles is then fed to a third solid-liquid separation unit.
The flash crystallizer used for concentrating the wastewater can take various forms, such as FC type, OSLO type, DTB type, DP type and the like which are commonly used in the crystallization field, and can be used for the flash crystallization operation of the step.
The flash evaporation crystallizer can be operated under normal pressure or negative pressure, preferably negative pressure, so that the flash evaporation of water and propylene glycol is facilitated, the operation temperature is reduced, and the corrosion of equipment under a high-temperature condition is avoided.
After the material containing larger crystal particles is sent into a solid-liquid separator, the solid organic acid salt is separated from liquid-phase propylene glycol and water, the liquid-phase propylene glycol and water are returned to a flash evaporation crystallizer, and the solid organic acid salt is difficult to separate out high-purity products due to complex components, so that the solid organic acid salt can be incinerated. Compared with the method for directly incinerating the epoxidized alkali washing wastewater, the method does not need a large amount of supplementary fuel to vaporize the wastewater, and can greatly save the operating cost of incineration treatment.
There are also many kinds of apparatuses for solid-liquid separation, such as centrifuges, filter presses, settling tanks, etc., and the present invention is preferably operated using a solid-liquid two-phase centrifuge.
(3) Dehydrating and refining the propylene glycol.
And (3) feeding the gas of the propylene glycol and the water flashed off in the operation of the step (2) into a propylene glycol dehydration tower, wherein water with the content of the propylene glycol less than or equal to 0.001% is obtained at the top of the tower, and crude propylene glycol with the content of the water less than or equal to 0.01% is obtained at the bottom of the tower.
Feeding the crude propylene glycol into a propylene glycol refining tower, extracting light components mainly comprising some unseparated water from the top of the tower in the propylene glycol refining tower, and returning the light components to a propylene glycol dehydration tower; heavy components, which mainly comprise some entrained salt and other heavy components, are extracted from the tower bottom and return to the flash evaporation crystallizer; and the 1, 2-propylene glycol product with the purity higher than 99.9 percent is extracted from the middle upper part of the propylene glycol refining tower.
The propylene glycol dehydrating tower and the propylene glycol refining tower are provided with 10-50 theoretical plates, and suitable tower plates can be bubble cap plates, floating valve plates, sieve plates, and regular packing or random packing.
The propylene glycol dehydration tower can be operated at 0.01-0.6 MPaA, preferably at 0.01-0.03 MPaA, so that the propylene glycol dehydration tower and the flash evaporator crystallizer in the step (2) can be operated in the same negative pressure system, and the investment of a vacuum system is saved.
The propylene glycol refining tower can be operated at 0.01-0.6 MPaA, preferably at 0.04-0.3 MPaA, and preferably adopts a thermal coupling mode, so that the energy consumption of the propylene glycol refining tower can be greatly reduced.
The invention has the beneficial effects that:
1. the propylene glycol in the propylene epoxidation alkaline washing wastewater is recovered by the method disclosed by the invention, the purity can reach the medical grade, and the economic benefit of the device can be increased;
2. most of propylene oxide, alcohol ketone, aromatic hydrocarbon and water in the wastewater can be recovered while the main product propylene glycol is recovered, so that the material consumption and desalted water consumption of the device are reduced;
3. the treatment cost of the organic acid salt can be greatly reduced, the fuel quantity sent into the incinerator is reduced, and the energy consumption of the device is reduced;
drawings
FIG. 1 is a flow diagram of a typical epoxidation wash caustic wash operation;
FIG. 2 is a flow chart showing the treatment of the epoxidized alkali washing wastewater in example 1;
FIG. 3 is a table comparing cost data for POSM wastewater treatment using the methods of example 1 and comparative example;
wherein, 01-alkali washing tank, 02-first-stage water washing tank and 03-second-stage water washing tank
G01-epoxidized material, G02-fresh alkali liquor, G03-desalted water or recovered fresh water, G04-washed material, G05-propylene epoxidation alkaline washing wastewater:
1-a flash tank, 2-a triple-effect evaporator, 3-a flash crystallizer, 4-a circulating pump, 5-a heater, 6-a centrifuge, 7-a propylene glycol dehydration tower and 8-a propylene glycol refining tower;
s01-epoxidized alkaline washing wastewater, S02-flash-off materials, S03-fresh water liquid extracted by a triple-effect evaporator, S04-concentrated wastewater, S05-gas phase material flow, S06-crystal slurry, S07-filtrate, S08-solid organic acid salt material flow, water liquid extracted by an S09-propylene glycol dehydrating tower, S10-propylene glycol material flow, light components extracted from the top of an S11-propylene glycol refining tower, S12-propylene glycol product material flow, heavy components extracted from the bottom of an S13-propylene glycol refining tower and S14-recovered fresh water material flow.
Detailed Description
The following examples further illustrate the present invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the invention may be made without departing from the spirit of the invention.
Example 1: 27/60 ten thousand ton/year epoxy propane/styrene coproduction device epoxy alkali washing waste water treatment method
The specific flow chart is shown in FIG. 2, the epoxidized alkaline washing wastewater S01 with the flow rate of 18233kg/h comes from an epoxidized alkaline washing unit, and comprises: 204kg/h of propylene oxide, 381kg/h of propylene glycol, 190kg/h of methylbenzyl alcohol and acetophenone, 21kg/h of ethylbenzene and 433kg/h of organic acid salt. Firstly, preheating epoxidation alkaline washing wastewater S01, then sending the wastewater into a flash tank 1, operating the flash tank 1 under the condition of micro-positive pressure, flashing most of propylene oxide, ethylbenzene and phenethyl alcohol (379kg/h), returning a flashed material S02 to a washing tank of an epoxidation device for recovering propylene oxide, ethylbenzene and phenethyl alcohol, and sending the wastewater remained in the flash tank 1 into a triple-effect evaporator 2.
In the triple-effect evaporator 2, about 94 percent of water in the wastewater is evaporated, all propylene oxide, ethylbenzene, methylbenzyl alcohol and acetophenone in the wastewater are evaporated along with water, and are condensed to form fresh water without salt, and the fresh water liquid S03 extracted by the triple-effect evaporator is returned to the step of washing the epoxidation materials, so that the propylene oxide, the ethylbenzene, the methylbenzyl alcohol and the acetophenone in the wastewater can be recovered, the water supplement amount of washing operation can be greatly reduced, and the discharge of the wastewater is reduced.
Due to the evaporation of the epoxypropane, the ethylbenzene, the methylbenzyl alcohol, the acetophenone and the water, substances with boiling points higher than that of the water, such as the propylene glycol, the organic acid salt and the like, are concentrated in the triple-effect evaporator 2, and then the concentrated wastewater S04 is discharged from the bottom of the triple-effect evaporator 2, wherein the concentration of the organic acid salt is controlled at 22%.
The concentrated wastewater S04 is mixed with filtrate S07 from a centrifuge 6 and circulating liquid discharged from a flash crystallizer 3, and then sent to a heater 5 to be heated to 100 ℃, and then enters the flash crystallizer 3, wherein the flash crystallizer 3 adopts a forced circulation FC type crystallizer. The operating pressure of the flash crystallizer 3 is 14kPaA, most of water and propylene glycol in the feed are subjected to flash evaporation and converted into a gas phase stream S05 (428 kg/h of propylene glycol and 1061kg/h of water) to enter a propylene glycol dehydrating tower 7; the content of the organic acid salt originally dissolved in the water phase exceeds the saturated solubility due to the evaporation of the solvent, crystals are formed and precipitated, and the crystals grow in the crystallizer. The grown crystal grains are settled to the bottom of the flash evaporation crystallizer 3, and the crystal slurry S06 is discharged from the flash evaporation crystallizer 3 and then is sent to a centrifuge 6; and fine crystal grains are suspended in a liquid phase, discharged from the side of the flash crystallizer 3, mixed with concentrated wastewater S04 and filtrate S07, and circulated by a circulating pump 4.
The slurry S06 containing the larger crystal particles enters centrifuge 6 by gravity difference and the crystals are separated from the liquid phase propylene glycol and water. The filtrate S07 discharged from the centrifuge 6 is propylene glycol and water from which crystals are removed, and is pressurized by a circulating pump 4 and then returned to the flash crystallizer 3 for continuous evaporation; and the solid organic acid salt material flow S08 is discharged from the centrifuge 6 and sent to an incinerator for incineration treatment. Because the solid organic acid salt material flow S08 is a solid phase, the solid organic acid salt material flow needs to be dissolved and then sent into the incinerator, other waste water in the device is preferentially adopted for dissolution, and in order to reduce the energy consumption of incineration treatment as much as possible, the content of the organic acid salt in the melted material is generally controlled to be 40-50%.
The gas phase material flow S05 flashed from the flash evaporation crystallizer 3 carries a large amount of water and is sent to a propylene glycol dehydration tower 7, the water contained in the gas phase material flow S05 is extracted from the top of the propylene glycol dehydration tower 7, a water liquid S09 extracted from the propylene glycol dehydration tower is mixed with a fresh water liquid S03 extracted from a triple-effect evaporator, and a recovered fresh water material flow S14 is returned to an epoxidation unit to be used as water supplement for water washing operation; the propylene glycol in the gas phase stream S05 is extracted from the bottom of the propylene glycol dehydration tower 7, and the propylene glycol content of the extracted propylene glycol stream S10 is 99%. Since the propylene glycol stream S10 extracted from the bottom of the propylene glycol dehydration column still contains incompletely separated water and entrained heavy components such as organic acid salts, the propylene glycol stream S10 is sent to the propylene glycol refining column 8 for further refining. In the propylene glycol refining tower 8, light components S11 extracted from the top of the propylene glycol refining tower mainly comprise some unseparated water, and the light components are returned to the propylene glycol dehydration tower 7 for continuous separation; heavy components S13 extracted from the bottom of the propylene glycol refining tower mainly comprise some entrained salt and other heavy components, but most of propylene glycol still returns to the flash crystallizer 3, the circulation amount is about 50kg/h, and finally the heavy components and salt enter a solid organic acid salt material flow S08 and are discharged from a discharge system for incineration treatment; and 378kg/h of propylene glycol product stream S12 with the purity higher than 99.9 percent is extracted from the middle upper part of the propylene glycol refining tower 8.
Example 1 is a preferred method of the invention for treating propylene epoxidation alkaline washing wastewater in a POSM device, which can produce 378kg/h of propylene glycol product, 204kg/h of propylene oxide, 190kg/h of methylbenzyl alcohol and acetophenone, 21kg/h of ethylbenzene, reduce desalted water consumption to 16t/h and reduce wastewater discharge to 16 t/h.
Comparative example
The output of the epoxidation alkaline washing wastewater S01 from 27/60 ten thousand tons/year propylene oxide/styrene cogeneration device is 18.2t/h, and 3540Nm is required by adopting the traditional incineration method3The natural gas is 3 yuan/Nm according to the price of the natural gas3The cost for treating each ton of wastewater is 583 yuan/ton, which is equivalent to the treatment cost of 500-600 yuan/ton reported in the literature. (Zhangxiong. high COD alkaline industrial wastewater treatment for propylene oxide production [ J]Chemical engineering and equipment, 2019, (8): 296-298).
FIG. 3 shows the comparative data of cost for POSM wastewater treatment using example 1 and comparative example, and from FIG. 3 it can be seen that the treatment of POSM wastewater using the method disclosed in example 1 not only reduces the treatment cost, but also creates economic benefits.
Example 2
The wastewater treatment process flow in this example is the same as that in example 1, but the epoxidation alkaline washing wastewater S01 is from a propylene oxide plant of 27 ten thousand tons/year cumene process.
The same method as the embodiment 1 is adopted to treat the epoxidation alkaline washing wastewater in the propylene oxide device by the cumene method, and the propylene glycol product can be produced at 370kg/h, the propylene oxide can be recovered at 196kg/h, the dimethylbenzyl alcohol and the acetophenone can be recovered at 50kg/h, the cumene can be recovered at 18kg/h, the desalted water consumption can be reduced by about 16t/h, and the wastewater discharge can be reduced by about 16 t/h. The comprehensive cost of each ton of wastewater treatment is-198 Yuan/ton.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. However, the above description is only an example of the present invention, the technical features of the present invention are not limited thereto, and any other embodiments that can be obtained by those skilled in the art without departing from the technical solution of the present invention should be covered by the claims of the present invention.
Claims (9)
1. A method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater is characterized by comprising the following specific operation flows:
(1) and (3) carrying out evaporation concentration on the epoxidation alkali washing wastewater: when the epoxidation alkali washing wastewater is evaporated and concentrated, firstly, normal-pressure flash evaporation is carried out, the materials flashed off are returned to be sent to the washing tank of the epoxidation device, then, the wastewater left in the flash evaporation tank is sent to the multi-effect evaporator again for negative-pressure evaporation, and the fresh water extracted by the multi-effect evaporation is returned to the step of washing the epoxidation materials;
(2) heating the concentrated wastewater generated in the step 1, and then feeding the heated concentrated wastewater into a flash evaporation crystallizer for crystallization to separate out organic acid salt crystals: mother liquor containing organic acid salt crystals is settled at the bottom of the crystallizer, the mother liquor containing a small amount of fine crystals at the upper part is pumped out and then is pressurized by a circulating pump together with concentrated wastewater, and the mother liquor is sent into a heater for heating and then is sent into a flash evaporation crystallizer for continuous crystallization; the lower part of the crystal slurry containing large crystal particles enters a solid-liquid separator, and separated liquid-phase propylene glycol and water are returned to a flash evaporation crystallizer;
(3) dehydration and refining of propylene glycol: and (3) feeding the water flashed out in the step (2) and propylene glycol into a propylene glycol dehydration tower to obtain crude propylene glycol, mixing water liquid extracted from the propylene glycol dehydration tower with fresh water liquid extracted from a multi-effect evaporator, feeding the recovered fresh water material flow back to an epoxidation unit as water supplement for water washing operation, feeding the crude propylene glycol into a propylene glycol refining tower, feeding light components extracted from the top of the tower back to the propylene glycol dehydration tower, feeding heavy components extracted from the bottom of the tower back to a flash evaporation crystallizer, and extracting a high-purity propylene glycol product from the middle upper part of the propylene glycol refining tower.
2. The method for recovering the propylene glycol and other organic matters from the propylene epoxidation alkaline washing wastewater as claimed in claim 1, wherein in the step (1), the multi-effect evaporator adopts 2-10-effect evaporation.
3. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater as claimed in claim 1, wherein the evaporation concentration operation in the step (1) is carried out stepwise under a pressure of 10 to 500 kPaA.
4. The method for recovering the propylene glycol and other organic matters from the propylene epoxidation alkaline washing wastewater as claimed in claim 1, wherein in the step (2), the flash evaporation crystallizer is operated under a negative pressure environment of 10-500 kPaA.
5. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkali washing wastewater as claimed in claim 1, wherein the concentration of organic acid salt in the concentrated wastewater generated after evaporation and concentration in step (1) is 10-50 wt%.
6. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater as claimed in claim 1, wherein the pressure of the propylene glycol dehydration tower is 0.01 to 0.6 MPaA.
7. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater as claimed in claim 1, wherein the pressure of the propylene glycol refining tower is 0.01-0.6 MPaA.
8. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater as claimed in claim 6, wherein the pressure of the propylene glycol dehydration tower is 0.01 to 0.03 MPaA.
9. The method for recovering propylene glycol and other organic matters from propylene epoxidation alkaline washing wastewater as claimed in claim 7, wherein the pressure of the propylene glycol refining tower is 0.04-0.3 MPaA.
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| EP1230169B1 (en) * | 1999-11-02 | 2003-07-30 | Shell Internationale Researchmaatschappij B.V. | Process for the purification of industrial waste water from a propylene oxide production process |
| US7002026B2 (en) * | 2004-06-21 | 2006-02-21 | Lyondell Chemical Technology, L.P. | Removal of propylene glycol and/or propylene glycol ethers from aqueous streams |
| US20090107919A1 (en) * | 2007-10-31 | 2009-04-30 | Chevron U.S.A. Inc. | Apparatus and process for treating an aqueous solution containing chemical contaminants |
| CN101693703B (en) * | 2009-10-14 | 2011-05-11 | 大连理工大学 | Energy-saving and emission-reducing technique for producing propane epoxide by using hydrogen peroxide epoxidation propylene |
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| CN203419863U (en) * | 2013-07-30 | 2014-02-05 | 天津大学 | Thermal coupling energy-saving system for reclaiming organic matters from propylene epoxidation waste water |
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