CN103012102A - Method of recovering acetic acid and water in production of aromatic carboxylic acid - Google Patents
Method of recovering acetic acid and water in production of aromatic carboxylic acid Download PDFInfo
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Abstract
A method of recovering acetic acid and water in the production of aromatic carboxylic acid adopts a separation technology of combined four towers which comprise an extracting tower, an azeotropic rectifying tower, a solvent extraction pro-tower and a solvent extraction tower connected orderly. The separation technology comprises the following steps: carrying out extraction, azeotropic distillation and solvent separation on the materials to obtain the water and the acetic acid, wherein the material with high water content is extracted first, then is combined with other materials for azeotropic distillation, the extraction and the azeotropic distillation adopt the same acetic ester separating agent, and the solvent recovery tower system adopts the compositive energy conservation combined technology. By adopting the method in the invention to separate and recover the acetic acid and water in the production of aromatic carboxylic acid, the organic matter in the water is less than or equal to 100ppm, the water and the acetic acid recovered can be used in the production system of aromatic carboxylic acid, thereby reducing the acid consumption and waste water discharge in the productive process. The method has low-cost separating agent, reasonable technology, is energy-saving and efficient in the separation process, and can save energy consumption by 20-30%, and reduce operating cost by 10-20%.
Description
Technical field
The present invention relates to a kind of method that in the aromatic carboxylic acid produces, reclaims solvent, particularly relate in a kind of aromatic carboxylic acid's the production process, adopt integrated energy saving separation technology to reclaim the method for acetic acid and water.
Background technology
Traditional aromatic carboxylic acid's production process adopts alkylaromatic hydrocarbon liquid phase air oxidation acquisition under the high pressure usually.The alkylaromatic hydrocarbon liquid-phase oxidation is in the presence of the aqueous media that contains the lower aliphatic carboxylic acid and metal catalyst system, and the alkyl on the aromatic hydrocarbons progressively oxidation generates aldehyde and carboxylic acid, finally obtains the aromatic carboxylic acid.
The oxidising process of alkylaromatic hydrocarbon will produce a large amount of heats, in order to keep the stable of reaction process temperature, usually adopt moisture lower aliphatic carboxylic acid (such as acetic acid) evaporation mode that heat is shifted out.The lower aliphatic carboxylic acid that shifts out and the mixture of water cool off by overhead condenser, then with condensed liquid solvent refluxing reactor recycling.Carrying out along with oxidizing reaction, the content of water will progressively increase in the reactor, be stablizing of moisture content in the maintenance reactor, usually with a part of refluxing reactor of the steam of reactor top condensation, a part enters the separation system of lower aliphatic carboxylic acid and water, after lower aliphatic carboxylic acid, water separated, the recycling of lower aliphatic carboxylic acid.In recent years, along with the raising that energy-saving and emission-reduction require, further reduce separating with energy of lower aliphatic carboxylic acid and water, improve the Separation of Water quality, more water can be recycled, become the focus that people pay close attention to.
In aromatic carboxylic acid's production process, the lower aliphatic carboxylic acid is as dissolution with solvents aromatic carboxylic acid and catalyzer, large usage quantity in production system, therefore, the consumption of lower aliphatic carboxylic acid is usually as one of index of controlling, and in order to improve the utilization ratio of water, how more rationally, efficient Separation of Water, the level that makes organic content in the water satisfy recycle just becomes key.
In aromatic carboxylic acid's production process, the most straight chain C that adopt of lower aliphatic carboxylic acid
2--C
6The unit carboxylic acid, such as acetic acid, propionic acid, butyric acid, isopropylformic acid, valeric acid and caproic acid, wherein acetic acid is the most frequently used solvent.But because acetic acid and water boiling point are more approaching, when acetic acid content was very low in the acetic acid water mixture, both sharply increased by separating difficulty.At present acetic acid and moisture from method have three kinds, common rectificating method, azeotropic distillation method and liquid-liquid extraction method.
In the production process of aromatic carboxylic acid's production process, particularly terephthalic acid, the rectifying separation of acetic acid and water, normally the multiply material of different production phases enters into rectifying tower, carry out acetic acid and moisture from, the cat head perfect condition is to obtain pure water, and is to obtain valuable acetic acid at the bottom of the tower.But because under high water concentration condition, acetic acid, steam liquid are the height non-ideal characteristic, therefore, for reaching high water purity, traditional distillation system needs a lot of number of theoretical plates, and the energy expenditure that causes is high.
For realizing minimumization of running cost, acetic acid content is controlled at usually greater than 0.8% in the overhead water of common rectifying tower.Owing to containing the organic by-products of higher concentration, usually can't carry out the water circuit recycling in these water, can only enter the waste water treatment plant as waste water and process.Therefore, traditional distillation system exists stage number many, and energy expenditure is large, and the separation purity of water is low, and the input construction cost is high, the problems such as process cost height.
In recent years, people more intend to develop the energy-saving rectifying novel process.Heterogeneous distillation technology is considered to a kind of more efficient energy-saving separation method and receives publicity.Heterogeneous distillation technology generally includes the separation method of liquid-liquid extraction and azeotropic distillation, liquid-liquid extraction technique separating acetic acid, the common report of water, usually it at 0.1-20% the aqueous solution, the extraction agent of employing is ester class, amine, ketone and phosphorus oxygen class for separating of acetic acid concentration.
Liquid-liquid extraction technique US3878241 and US5167744 describe to some extent.US3878241 be with 1,2-dimorpholine ethane as extraction agent, separate the acetic acid solution of 50% (wt) with the extractive distillation column of 23 blocks of column plates, tower top pressure 0.5 normal atmosphere.The maximum characteristics of this patent are can make to contain acetic acid in the overhead product water and be controlled at 0.01% (wt).US5167744 is with dimethyl sulfoxide (DMSO), tetramethylene sulfone, dimethyl formamide, dimethyl propylene acid amides, the compound of the nitrogenous or sulfur-bearing such as dintrile is as extraction agent, the principal feature of invention is that the nitrogenous compound of selecting has very high relative volatility, be used for the sepn process of acetic acid water, can realize that knockout tower cat head acetic acid content is less than 1% target.
People are devoted to seek more efficiently separation means, compare with traditional rectifying, and azeotropic distillation is in the dehydration of acetic acid separates, but conserve energy 20-40%.Azeotropic distillation technique is for separating of the method for acetic acid, water, and US2050234, US4250330, CN1907940A, CN101445444A, CN101312936A describe to some extent.Patent GB1576787 thinks that n-butyl acetate (126.2 ℃ of boiling points) is particularly suitable for the separation of acetic acid, water, and this is because it can make the azeotropy rectification column backflow smaller, has so just reduced and has separated required energy.Patent thinks, from the angle of reflux ratio, is not suitable for the azeotrope that adopts boiling point relatively low, such as isobutyl acetate (117 ℃ of boiling points).
In aromatic carboxylic acid's production process, because the acetic acid that rectifying tower separates part will be back to the carboxylic acid oxidative reactive system, therefore, can contain the water about 5% in the acetic acid that separates at the bottom of the final rectifying tower.US4250330 considers the factor of this respect, thinks that the component water-content adopts isobutyl acetate to have better effect as entrainer under the 5-10% condition at the bottom of tower.Patent US4250330 does not wish to adopt n-propyl acetate (101 ℃ of boiling points), and patent is thought because the use of n-propyl acetate is entrained in the complex compound a lot of water, therefore, and the preferred isobutyl acetate of patent.
The CN101445444A patent be take n-propyl acetate on the basis of entrainer rectifying tower, set up an extraction tower, make the water of azeotropic distillation column overhead before entering the solvent recovery tower of back, extract first, to extract acid and ester class wherein.The method has reduced the segregational load of follow-up solvent recovery tower, has saved energy.
The CN101312936 patent consider enter acetic acid moisture from the composition of material stream change greatly, proposed in the anterior processing method that increases extraction tower of azeotropy rectification column.Adopt the material that this method can be larger with partially aqueous concentration to carry out the concentrate processing, reduced the process cost of sepn process.Combined azeotropy distillation tower and extraction tower, the agent of patent preferable separation is isobutyl acetate, n-butyl acetate, isopropyl acetate, n-propyl acetate.Organic content is generally 600-1000ppm in the azeotropic distillation cat head water, and wherein acetic acid content is at 500-800ppm.
CN1907940 considers and enters the p-Xylol that contains in the rectifying tower material stream, owing to being difficult in sepn process, remove, cause the production operation expense to rise, and the entrainer outside the employing system has increased the pollution to system, in the production owing to adopting ester class entrainer, so that carry the part alcohol compound in the separation of material secretly, the accumulation of these materials in rectifying tower, increased acetic acid moisture from difficulty and the effect of separating.Patent thinks that adopting aromatic hydrocarbons is that the sepn process of entrainer can well address the above problem.The preferred p-Xylol of its Patent as acetic acid, moisture from entrainer, but, because the compounds such as methyl acetate that azeotrope and aromatic carboxylic acid's production process produce also more easily form azeotrope, therefore, separating needs to adopt than high reflux ratio, and consumed energy is larger, simultaneously, organic content is higher in the rectifying tower top water, and wherein acetic acid content will be greater than 0.5%.
In above-mentioned azeotropic distillation patented technology, in order to recycle overhead water, the water material after usually azeotropic distillation being separated enters the solvent recovering system separating-purifying.Because aqueous phase contains water, acetic acid and three components of entrainer, therefore, for reaching the separation purpose, solvent recovering system need to adopt two tower rectification process, and each tower all is equipped with reboiler and condenser.At first the water material enters into tower before the solvent recuperation, obtains water at the bottom of the tower, and the cat head material enters solvent recovery tower through after the condensation, and cat head obtains methyl acetate, at the bottom of the tower to entrainer.But, generally, have all that the acetic acid rate of recovery is low, steam consumption too much and the drawbacks such as the high wastewater flow rate that produces owing to acetic acid, the methyl acetate of Coal Gas Washing Cycling Water and great number wastewater treatment expense.And unreacted aromatic hydrocarbons enters dewatering unit in the feedstream thigh, causes aromatic carboxylic acid's low-yield.In the azeotropic distillation cat head aqueous solution, acetic acid content also is merely able to be controlled at 500-800ppm, can't satisfy the target of water circulation use.
At present in aromatic carboxylic acid's suitability for industrialized production, tend to adopt in the oxidizing reaction low water content solvent, water that should produce of will negating is more shifts out from reactor for these, just means that also the water-content in the stream thigh that enters acetic acid, water rectifying tower will increase, and has also increased the lock out operation expense.Therefore, need to further reduce organic content in the water reducing separation with in the energy, improve the utilization ratio of water.
Summary of the invention
The object of the present invention is to provide a kind of method that from aromatic carboxylic acid's production process, reclaims acetic acid and water, particularly in the Production of Terephthalic Acid process, recycle the method for acetic acid and water, the inventive method can reduce organic content in the water, advantage with less energy-consumption, lower operational cost can be used for the transformation of the existing azeotropic distillation of aromatic carboxylic acid's production process or the construction of novel production equipment.
The technical solution adopted in the present invention is as follows:
Reclaim the method for acetic acid and water during a kind of aromatic carboxylic acid produces, it is characterized in that:
Adopt the separating technology of four towers combination, comprise the front tower of extraction tower, azeotropy rectification column, solvent extraction and solvent extraction tower that order links to each other, material to be separated obtains water and acetic acid through extraction, azeotropic distillation and separated from solvent;
Described method may further comprise the steps:
1) material of water-content 〉=45% carries out extracting and separating through extraction tower, adopting the acetic ester of boiling point between sec-butyl acetate and n-propyl acetate boiling point is extraction agent, and cat head is the extraction agent of rich long-pending acetic acid, enters azeotropy rectification column, be rich water raffinate stream at the bottom of the tower, enter the front tower of solvent extraction;
2) material of water-content 10-45% directly enters azeotropy rectification column, carrying out azeotropic distillation with the cat head material of step 1) in azeotropy rectification column separates, after the phase-splitting of azeotropy rectification column overhead condensation liquid, the organic phase partial reflux is to the azeotropic distillation column overhead, part circulates as extraction agent and returns extraction tower, enters the front tower of solvent extraction after water and step 1) extraction tower materials at bottom of tower merge; Materials at bottom of tower is for reclaiming acetic acid;
3) step 1) extraction tower materials at bottom of tower and step 2) water of azeotropy rectification column overhead condensation liquid enters tower before the solvent extraction after merging, tower and solvent extraction tower form the solvent recuperation Tower System before the solvent extraction, wherein tower is not established condenser and reboiler before the solvent extraction, shares reboiler and the condenser of solvent recovery tower; The tower materials at bottom of tower directly enters solvent recovery tower before the solvent extraction, and behind steam heat-shift in the solvent recovery tower, part steam enters tower bottom before the solvent extraction; Column overhead steam directly enters solvent recovery tower before the solvent extraction, and behind phegma heat-shift in the solvent recovery tower, partial reflux liquid enters top of tower before the solvent extraction; After solvent recovery tower separates, recycle-water at the bottom of the tower.
Described extraction agent comprises one or more in sec-butyl acetate, n-propyl acetate, n-butyl acetate or the isobutyl acetate.
Described entrainer adopts the organism identical with extraction agent.
The combination process of four-column process flow of the present invention comprises extraction tower, azeotropy rectification column, the front tower of solvent extraction and solvent extraction tower.Arranging of extraction tower mainly is stream thigh material for separating of different water-contents, to reach the reduction operation cost, saves the purpose of separating with energy.
At first with water-content 〉=45%, the material stream that is generally the 45-70% water-content enters the top of extraction tower, and contact with the extraction agent that upwards flows from extraction tower bottom, the organism such as acetic acid, micro-reaction by product such as methyl acetate that extraction wherein contains, rich water raffinate stream at the bottom of the extraction tower directly enters the solvent extraction Tower System behind the azeotropy rectification column, the material at extraction tower top is mainly extraction agent, wherein contain micro-by product (methyl acetate) and acetic acid, the material stream of amassing acetic acid as richness enters azeotropy rectification column.And water-content to be the stream thigh material of 10-45% directly enter azeotropy rectification column, in azeotropy rectification column by and the azeotrope that forms of entrainer, reach separating of acetic acid under more low-yield and water.
The present invention further improves acetic acid and moisture from efficient and reduces the method for operation cost, that extraction and azeotropic distillation adopt separating agent unified, with low cost, reduced like this production process interference, simplification of flowsheet and equipment have reduced the difficulty of separating; Simultaneously, separating agent with low cost obviously reduces running cost under identical consumption consumption.Described separating agent (extraction agent and entrainer) is sec-butyl acetate, n-propyl acetate or the acetic ester of other boiling point between sec-butyl acetate and n-propyl acetate, such as n-butyl acetate or isobutyl acetate, preferably sec-butyl acetate.
Described azeotropy rectification column materials at bottom of tower reclaims acetic acid, and its water-content is 5-10%, can be back to the recycle of carboxylic acid oxidative reactive system.
It is to the acetic acid behind extraction and/or azeotropic distillation and the further separating-purifying of water mixture the time from the method for efficient that the present invention further improves acetic acid and moisture, adopt the solvent recuperation Tower System of integrated two towers combination, condenser and the reboiler of tower before the cancellation solvent extraction.The inventive method is to utilize in the solvent recovery tower phegma in the tower before the rising steam and solvent extraction, and the overhead vapours of tower contacts with phegma in the solvent recovery tower before the solvent extraction, carries out the exchange of heat and quality.After the solvent recuperation Tower System separated, each material stream after the solvent extraction tower extraction separates obtained highly purified recycle-water at the bottom of the tower, and wherein organic content is to 100ppm or still less in the water.
The extraction of solvent extraction tower organic constituents can be taked dual mode, and a kind of mode is the mixture that the solvent extraction column overhead obtains organic by-products (such as methyl acetate) and entrainer; Another kind of mode is that solvent extraction tower arranges side line discharge, and cat head obtains organic by-products (methyl acetate), and the middle part side line discharge obtains entrainer.Entrainer after solvent extraction tower separates is delivered to the azeotropy rectification column recycle.
The method that the present invention further improves separating effect again is in azeotropy rectification column, adopts efficient structured packing column internals replacing plate formula filler, and tower height obviously reduces like this.Adopt 71 blocks of column plates such as traditional plate distillation column, and be 45 blocks of theoretical trays with sec-butyl acetate as the azeotropy rectification column of entrainer, employing structured packing.
Advantage of the present invention is as follows:
1) technique that adopts four tower process to make up, being suitable for Separation of Water content is the stream thigh material of 10-70%.
2) the stream thigh material of different water-contents adopts different treatment process, the material that wherein water content is higher extracts first, carries out azeotropic distillation after the organism enrichment wherein again, and the material that water content is lower directly carries out azeotropic distillation, use energy to reduce operation cost, to save to separate.
3) extraction adopts identical organism as extraction agent and entrainer with azeotropic distillation, and recycles in technical process.
4) the azeotropic distillation column overhead is separated the extraction agent partial reflux obtain to the azeotropic distillation column overhead, water enters the solvent recuperation Tower System of two towers combination, the solvent recuperation Tower System adopts integrated energy-saving technique, and organic content is about 100ppm in solvent recuperation bottoms material-water.
Adopt Separation and Recovery acetic acid of the present invention and water, can obtain acetic acid and water that aromatic carboxylic acid's production system is accepted, the organic amount that wherein contains in the water is about 100ppm or still less; Simultaneously, produce the entrainer that adopts low-cost, the production operation expense is reduced greatly; Again, compare with azeotropic distillation method of the prior art, greatly reduce reboiler and the required energy of condenser reach separate targets, further conserve energy 30-50% on the basis of azeotropic distillation.
In a word, acetic acid and water during the inventive method Separation and Recovery aromatic carboxylic acid produces, organic content≤100ppm in the water all can utilize in aromatic carboxylic acid's production system with recovery acetic acid, has reduced acid consumption and the wastewater discharge of production process; The separating agent cost is low, and technique is reasonable, and sepn process is energy-conservation, efficient, and the production process energy expenditure is saved 20-30%, and process cost reduces 10-20%.
Description of drawings
Fig. 1 is one of schema of acetic acid and water during four-column process flow aromatics separation carboxylic acid of the present invention is produced.
Fig. 2 be acetic acid and water during four-column process flow aromatics separation carboxylic acid of the present invention is produced schema two.
Embodiment
Describe the present invention below in conjunction with accompanying drawing.Protection scope of the present invention is not limited with embodiment, but is limited by claim.
Fig. 1 and Fig. 2 are the acetic acid of four-column process flow of the present invention and the separation and recovery method process flow diagram of water, and the raw material of separation comes from respectively preparing aromatic hydrocarbon carboxylic acid oxidative reactor head phlegma and extracts part, crystallizer overhead vapor etc. out.
Because water-content is different in the pending material that produces in different steps, therefore, at least one material stream 1 that water-content is high joins in the extraction tower 601 from the top, in extraction tower 601 by with flow automatically strands 9 the reverse MULTI CONTACT of extraction agent, the organism such as acetic acid in the stream thigh 1 are progressively rich long-pending in extraction agent, at last form the material stream 2 that mainly contains acetic acid, extraction agent at extraction tower 601 tops, the by product that wherein also comprises micro-oxidizing reaction, such as the methyl acetate in the Production of Terephthalic Acid, then material 2 enters azeotropy rectification column 602.
The extraction agent stream strands 9 that enters extraction tower 601 from the bottom by azeotropy rectification column 602 top decanting vessels 8 in part oil phase stream strands 92 and the extraction agent 93 that replenishes mix and form.For reaching better separating effect, mix the extraction agent stream that forms strands 9 and can flow automatically and strands 92 form with two kinds of different extraction agents of 93, also can utilize the entrainer in the azeotropy rectification column 602.The mode that the present invention recommends is the entrainer that utilizes in the azeotropy rectification column, and described entrainer can be n-propyl acetate, n-butyl acetate, isobutyl acetate or sec-butyl acetate.The better sec-butyl acetate of separation performance that has adopted in an embodiment the present invention to recommend.
Directly enter azeotropy rectification column 602 from other stream thigh 3 and stream thigh 4 in aromatic carboxylic acid's production process.
In azeotropy rectification column 602, because entrainer and the water capacity easily form lower boiling azeotrope, therefore, changed the relative volatility in azeotropy rectification column 602 interior acetic acid and the steam liquid phase, thereby realized more easily separating of acetic acid and water.The heat that azeotropy rectification column 602 separates comes from the reboiler 50 at the bottom of the tower, by reboiler 50 with azeotropy rectification column 602 towers at the bottom of the heating vaporization of liquid material 52 parts, form rising steam material 51, the heat hot load can be determined by separated from acetic acid purity in the materials at bottom of tower 5.
The steam of azeotropy rectification column 602 interior risings contacts step by step with reflux in tower liquid, and conduct heat, mass transfer process, at last at azeotropy rectification column 602 cats head, vapour stream thigh 6 enters evaporator overhead condenser 60 and carries out the phase transformation thermal exchange.Stream strands 7 enters decanting vessel 8 with liquid form after the condensation, and the lower boiling azeotrope phlegma of formation is in decanting vessel 8 interior stand at low temperature layerings, and the concentration of azeotrope component is redistributed, and forms oil, the water two-phase of obvious layering.The oil phase of light constituent places decanting vessel 8 upper stratas, mainly contain entrainer, organic by-products, these liquid parts are back to azeotropy rectification column 602 cats head by stream thigh 91, a part of stream strands 92 and the extraction agent stream that replenishes strands 93 mixes in addition, flows thigh 9 as extraction agent and enters extraction tower 601 from extraction tower 601 bottoms.
Restructuring in the azeotropy rectification column 602 top phlegmas divides water, contains water, organic by-products, a small amount of entrainer and micro-acetic acid.For obtaining the low water of organic content, and to wherein entrainer and organic by-products, recycle such as methyl acetate, the present invention adopts the solvent recuperation Tower System of double tower combination further to separate.
As shown in Figure 1, the aqueous phase stream thigh 11 that at first will recombinate minute and the rich water raffinate stream thigh of extraction tower 601 10 mix, and then enter tower 603, Separation of Water and organism before the solvent recuperation with several stage number.Separate for saving with can, tower 603 tower bottoms stream thighs 24 directly enter solvent recovery tower 604 before the solvent recuperation, behind steam heat-shift in the solvent recovery tower 604, the part steam of generation enters tower 603 before the solvent recuperation by stream strands 23; Equally, separate with energy for saving, tower 603 vapor stream of top of the tower thighs 22 are without original condenser before the solvent recuperation, directly enter solvent recovery tower 604, tower 603 before partial condensation liquid 21 reflux solvents reclaim, and the solvent recovery tower entire system that the front tower 603 of solvent recuperation and solvent recovery tower 604 form shares a reboiler 61 and a condenser 62.Solvent recovery tower 604 bottoms can obtain stream thigh 31, are the water of organic content less than 100ppm.Solvent recovery tower 604 recovered overhead entrainer and organic by-products except through overcurrent thigh 33 partial reflux, enter decanting vessel 8, backflow azeotropy rectification column 602 tops by stream thigh 32.
The another kind of implementation method of solvent recuperation Tower System, technique as shown in Figure 2, the rich water raffinate stream thigh 10 of the aqueous phase stream thigh 11 that divides recombinating and process extraction tower 601 extraction treatment mixes, then enter the front tower 603 of solvent recuperation, separate through tower 603 before having the solvent recuperation of several stage number, will enter before the solvent recuperation that water separates with other organism in tower 603 materials.Separate for saving with can, tower 603 tower bottoms stream thigh 15(are rich in water before the solvent recuperation) directly enter solvent recovery tower 604, behind steam heat-shift in the solvent recovery tower 604, the part steam of generation enters tower 603 before the solvent recuperation by stream strands 14; Equally, separate with energy for saving, tower 603 vapor stream of top of the tower thighs 13 are without original condenser before the solvent recuperation, directly enter solvent recovery tower 604, tower 603 before partial condensation liquid 12 reflux solvents reclaim, and the solvent recovery tower entire system that the front tower 603 of solvent recuperation and solvent recovery tower 604 form shares a reboiler 80 and a condenser 90.Solvent recovery tower 604 bottoms can obtain stream thigh 18, are the water of organic content less than 100ppm.For with different organism according to different purposes recyclings, adopt the lateral line discharging mode at solvent recovery tower 604, extract in the middle separation and obtain entrainer, this strand material 17 enters decanting vessel 8 reuses, and cat head is except through overcurrent thigh 16 partial reflux, can obtain organic by-products stream thigh 19, such as methyl acetate, can directly as international sale, also can be back in the oxidation reactor, the carrying out of inhibited oxidation process combustion reactions, thereby Reduction of acid consumption.
Because wherein organic content is significantly less than organic content (600-900ppm) level in the water that traditional azeotropic distillation obtains, therefore aforesaid method separates the water that obtains and can circulate in utilization in aromatic carboxylic acid's production system, thereby greatly reduces the consumption of water.And the content of organic compound acetic acid reduces in the water, has improved production of units aromatic carboxylic acid's solvent rate of utilization, has reduced sour consumption.
Compare with traditional azeotropic distillation technology, acetic acid moisture of the present invention is from the method that reclaims, and have following advantage: 1) the production process energy expenditure will be saved 20-30%.2) produce the entrainer that adopts, because low cost makes the production operation expense reduce 10-20%; 3) organic content in the water of separating-purifying not only makes quantity of wastewater effluent reduce more than 15%, has reduced simultaneously the acid consumption of production process.
Following instance compares separation method and the inventive method of acetic acid in the prior art and water.In the description of Comparative Examples, part contrast shown in Figure 1 flow process and the Reference numeral similar to the present invention describes, and distinct portions will be pointed out in description.
Comparative Examples 1
Need to carry out acetic acid, moisture from three stream stocks not from the different unit of Production of Terephthalic Acid system, wherein stream strand 1,3,4 processing parameters are as shown in table 1 below.According to strand different material state of each stream and the concentration of water, separately feed entrance point sees Table shown in 1 in traditional azeotropy rectification column 602.At azeotropy rectification column 602 cats head by stream gang 93(without extraction tower) carry out replenishing of entrainer sec-butyl acetate, the top gaseous phase component is condensed into liquid phase through condenser 60, then in decanting vessel 8, carry out leaving standstill and layering of heterogeneous liquid, decanting vessel 8 interior oil phases all are back to azeotropy rectification column 602 tops after the layering, and the water material 35% be back to azeotropy rectification column 602 tops, remaining material of 65% enters the solvent recuperation Tower System (double tower is respectively equipped with reboiler and condenser) that two towers form.It is tower 603 before 10 the board-like solvent recuperation that the water material is introduced into stage number, and wherein charging is at the 6th block of column plate.Separation by tower before the solvent recuperation 603, obtaining purity at the bottom of the tower is 99.8% water, and overhead product enters solvent recovery tower 604 further separation to reclaim extraction agent, enters solvent recovery tower 604 the 10th column plate position, and solvent recovery tower 604 total stage number are 23.Obtain mass concentration and be 95% acetic acid solution at the bottom of azeotropy rectification column 602 stills, this burst solution circulated recycles in production system.
Whole system is separated related data and is seen Table 3.
Table 1
Comparative Examples 2
Change the entrainer that adopts into isobutyl acetate, wherein stream strand 1,3,4 processing parameters are as shown in table 2 below.Other implementation processes are with Comparative Examples 1, and whole system is separated related data and seen Table 3.
Table 2
Comparative Examples 3
Stream thigh 1 in the Comparative Examples 1 is introduced into preposition extraction tower 601 pre-separations, and extraction agent and entrainer all adopt sec-butyl acetate, other implementation processes are with Comparative Examples 1, and whole system is separated related data and seen Table 3.
Embodiment 1
Adopt flow process shown in Figure 2, stream thigh 1 among the embodiment 1 is introduced into preposition extraction tower 601 pre-separations, and extraction agent and entrainer all adopt sec-butyl acetate, simultaneously when azeotropy rectification column 602 cat head waters extraction component is carried out solvent recuperation, adopt technique of the present invention, be the cat head of tower 603 before the board-like solvent recuperation and the 10th and the 20th block of column plate that bottom product enters respectively solvent recovery tower 604, simultaneously, increase side line discharge in the 14th column plate position of solvent recovery tower 604, extract stream thigh 17 out, be used for extracting out the entrainer of high density.Whole system is separated related data and is seen Table 3.
Process systems different in the above-mentioned example is carried out analog calculation, according to the calculation result under the different process, compare the superiority of technique of the present invention.Specifically compare content and the results are shown in Table 3.
From the results shown in Table 3, adopt sec-butyl acetate in traditional azeotropy rectification column, although the reboiler thermal load increases by 2.7%, the entrainer of use hour total expenses reduces by 26% than isobutyl acetate, and process cost is lowered.And the scheme of employing Comparative Examples 3, because the high stream thigh of water-content is carried out extracting and enriching to be processed, greatly reduce like this separation burden of azeotropy rectification column, compare with Comparative Examples 1, the thermal load of reboiler reduces nearly 26.8% at the bottom of the azeotropic distillation tower reactor, and in conjunction with the thermal load of tower before the solvent recuperation and solvent recovery tower, it reduces energy expenditure and reaches 21%.Adopt the result of the embodiment 1 that technique of the present invention carries out to show, the thermal load of reboiler reduces closely 26.8% at the bottom of the azeotropic distillation tower reactor, and the steam consumption of solvent recuperation Tower System reduces 20%, and whole separation system energy expenditure reduces 32.5%.
In addition, from separating effect, separate in the water that obtains in Comparative Examples 1 and the Comparative Examples 2, acetic acid content is substantially at 700ppm.Comparative Examples 3, can be further with the content of acetic acid in the water at 200ppm.Adopt technique of the present invention, the content of acetic acid meets approximately 100ppm in the water of final Separation and Recovery, basically can recycle and reuse, greatly reduce because the consumption of the acetic acid that original discharge of wastewater causes, and also alleviated the processing load of waste water.
Table 3
The above embodiment only is that protection scope of the present invention is not limited to above-mentioned specific embodiment for explanation the present invention enumerates.What those skilled in the art did on the basis of described embodiment is equal to or equivalent substituting or conversion, all within protection scope of the present invention.Protection scope of the present invention is as the criterion with claims.
Claims (10)
1. reclaim the method for acetic acid and water during an aromatic carboxylic acid produces, it is characterized in that:
Adopt the separating technology of four towers combination, comprise the front tower of extraction tower, azeotropy rectification column, solvent extraction and solvent extraction tower that order links to each other, material to be separated obtains water and acetic acid through extraction, azeotropic distillation and separated from solvent;
Described method may further comprise the steps:
1) material of water-content 〉=45% carries out extracting and separating through extraction tower, adopting the acetic ester of boiling point between sec-butyl acetate and n-propyl acetate boiling point is extraction agent, and cat head is the extraction agent of rich long-pending acetic acid, enters azeotropy rectification column, be rich water raffinate stream at the bottom of the tower, enter the front tower of solvent extraction;
2) material of water-content 10-45% directly enters azeotropy rectification column, carrying out azeotropic distillation with the cat head material of step 1) in azeotropy rectification column separates, after the phase-splitting of azeotropy rectification column overhead condensation liquid, the organic phase partial reflux is to the azeotropic distillation column overhead, part circulates as extraction agent and returns extraction tower, enters the front tower of solvent extraction after water and step 1) extraction tower materials at bottom of tower merge; Materials at bottom of tower is for reclaiming acetic acid;
3) step 1) extraction tower materials at bottom of tower and step 2) water of azeotropy rectification column overhead condensation liquid enters tower before the solvent extraction after merging, tower and solvent extraction tower form the solvent recuperation Tower System before the solvent extraction, wherein tower is not established condenser and reboiler before the solvent extraction, shares reboiler and the condenser of solvent recovery tower; The tower materials at bottom of tower directly enters solvent recovery tower before the solvent extraction, and behind steam heat-shift in the solvent recovery tower, part steam enters tower bottom before the solvent extraction; Column overhead steam directly enters solvent recovery tower before the solvent extraction, and behind phegma heat-shift in the solvent recovery tower, partial reflux liquid enters top of tower before the solvent extraction; After solvent recovery tower separates, recycle-water at the bottom of the tower.
2. the method for recovery acetic acid according to claim 1 and water, it is characterized in that: described extraction agent is one or more in sec-butyl acetate, n-propyl acetate, n-butyl acetate or the isobutyl acetate.
3. the method for recovery acetic acid according to claim 2 and water, it is characterized in that: described extraction agent is sec-butyl acetate.
4. the method for recovery acetic acid according to claim 1 and water is characterized in that: the described entrainer employing organism identical with extraction agent.
5. the method for recovery acetic acid according to claim 1 and water is characterized in that: described azeotropy rectification column materials at bottom of tower is for reclaiming acetic acid, and its water-content is 5-10%.
6. the method for recovery acetic acid according to claim 1 and water is characterized in that: at the bottom of the solvent extraction tower tower in the recycle-water, and organic content≤100ppm.
7. the method for recovery acetic acid according to claim 1 and water is characterized in that: solvent extraction tower overhead extraction entrainer.
8. the method for recovery acetic acid according to claim 1 and water is characterized in that: solvent extraction tower middle part side line extraction entrainer.
9. it is characterized in that according to claim 7 or the method for 8 described recovery acetic acid and water: the entrainer after solvent extraction tower separates is delivered to the azeotropy rectification column recycle.
10. the method for recovery acetic acid according to claim 1 and water is characterized in that: in the described azeotropy rectification column, adopt the structured packing column internals.
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| WO2016055463A1 (en) * | 2014-10-06 | 2016-04-14 | Invista Technologies S.À R.L. | Method for removing residues by means of a stripping device |
| CN110088074A (en) * | 2016-12-22 | 2019-08-02 | 庄信万丰戴维科技有限公司 | The method for purifying unsaturated carboxylic acid |
| CN112374676A (en) * | 2020-10-22 | 2021-02-19 | 江苏扬农化工集团有限公司 | Device and method for separating and purifying byproducts in epichlorohydrin wastewater |
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| CN103012102B (en) | 2014-09-17 |
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