CN109761425B - Separation and recovery system for NMP in salt-containing solution - Google Patents
Separation and recovery system for NMP in salt-containing solution Download PDFInfo
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- CN109761425B CN109761425B CN201910091113.XA CN201910091113A CN109761425B CN 109761425 B CN109761425 B CN 109761425B CN 201910091113 A CN201910091113 A CN 201910091113A CN 109761425 B CN109761425 B CN 109761425B
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- 238000011084 recovery Methods 0.000 title claims abstract description 84
- 150000003839 salts Chemical class 0.000 title claims abstract description 43
- 238000000926 separation method Methods 0.000 title abstract description 15
- 238000000605 extraction Methods 0.000 claims abstract description 85
- 239000012266 salt solution Substances 0.000 claims abstract description 59
- 239000002699 waste material Substances 0.000 claims abstract description 33
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000000243 solution Substances 0.000 claims abstract description 22
- 238000001704 evaporation Methods 0.000 claims abstract description 15
- 230000008020 evaporation Effects 0.000 claims abstract description 14
- 238000003860 storage Methods 0.000 claims description 89
- 238000010438 heat treatment Methods 0.000 claims description 37
- 239000012452 mother liquor Substances 0.000 claims description 31
- 238000010992 reflux Methods 0.000 claims description 18
- 239000011347 resin Substances 0.000 claims description 15
- 229920005989 resin Polymers 0.000 claims description 15
- 238000005406 washing Methods 0.000 claims description 15
- 238000002425 crystallisation Methods 0.000 claims description 10
- 230000008025 crystallization Effects 0.000 claims description 10
- 238000000746 purification Methods 0.000 claims description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 239000002904 solvent Substances 0.000 abstract description 28
- 238000004064 recycling Methods 0.000 abstract description 8
- 239000007788 liquid Substances 0.000 abstract description 2
- 239000011259 mixed solution Substances 0.000 abstract description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 124
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 29
- 238000000034 method Methods 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 8
- 238000004821 distillation Methods 0.000 description 6
- 229920003366 poly(p-phenylene terephthalamide) Polymers 0.000 description 6
- 230000007062 hydrolysis Effects 0.000 description 5
- 238000006460 hydrolysis reaction Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 5
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- 229920003235 aromatic polyamide Polymers 0.000 description 4
- 239000012267 brine Substances 0.000 description 4
- 239000003456 ion exchange resin Substances 0.000 description 4
- 229920003303 ion-exchange polymer Polymers 0.000 description 4
- 238000006116 polymerization reaction Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 4
- 239000007864 aqueous solution Substances 0.000 description 3
- 238000009833 condensation Methods 0.000 description 3
- 230000005494 condensation Effects 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 238000000197 pyrolysis Methods 0.000 description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- 239000001110 calcium chloride Substances 0.000 description 2
- 229910001628 calcium chloride Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 239000006184 cosolvent Substances 0.000 description 2
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- 230000006837 decompression Effects 0.000 description 2
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- HCSCWJCZRCSQFA-UHFFFAOYSA-N 1-methylpyrrolidin-2-one;hydrate Chemical compound O.CN1CCCC1=O HCSCWJCZRCSQFA-UHFFFAOYSA-N 0.000 description 1
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 description 1
- 229920006231 aramid fiber Polymers 0.000 description 1
- -1 aromatic haloalkane Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- HIKUCVORZZXYNF-UHFFFAOYSA-L calcium;1-methylpyrrolidin-2-one;dichloride Chemical compound Cl[Ca]Cl.CN1CCCC1=O HIKUCVORZZXYNF-UHFFFAOYSA-L 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
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- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000011033 desalting Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000000909 electrodialysis Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
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- 238000003786 synthesis reaction Methods 0.000 description 1
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- Extraction Or Liquid Replacement (AREA)
Abstract
The invention belongs to the technical field of mixed solution recovery devices, and particularly relates to a separation and recovery system for NMP in a salt-containing solution. Mainly comprises an extraction device, a stripping tower, an extractant removing device, an NMP purifying device and an evaporating device. The recovery system adopts dynamic extraction at normal temperature, not only realizes the separation of the solvent and water, but also greatly improves the recovery rate of the solvent, and ensures that the recovery rate of the solvent reaches more than 99.95 percent; the evaporation device is used for recycling the salt in the waste salt solution, so that the recycling of the salt solution is realized, the cost is reduced, the low emission of waste liquid is realized, and the national environment-friendly requirement is met.
Description
Technical Field
The invention belongs to the technical field of mixed solution recovery devices, and particularly relates to a separation and recovery system for NMP in a salt-containing solution in a para-aramid production process.
Background
In the process of producing synthetic PPTA resin by using aramid fiber, low-temperature polycondensation reaction is required to be carried out in an organic solvent which takes NMP (N-methylpyrrolidone) as a solvent and calcium chloride as a cosolvent, a large amount of hydrochloride is generated after neutralization of hydrochloric acid generated in the reaction process, the main product PPTA resin is obtained by washing reaction liquid after the reaction is finished, the water consumption in the washing process of the PPTA resin is usually large, and the neutralized solution is an aqueous solution containing a large amount of organic solvent and salt, wherein the water contains a large amount of NMP and calcium chloride, so that if the solution is directly abandoned, not only is a large amount of waste caused, but also the production cost is increased, and meanwhile, the discharge of untreated wastewater also causes the problem of environmental pollution.
Chinese patent CN101457414 mentions a combined desalting-distillation method for separating and recovering NMP, salt, water mixed solvent system, specifically using electrodialysis or ion exchange resin to remove salt dissolved in the neutralization recovery liquid, and then separating water from NMP by distillation. The method needs a film or ion exchange resin with good performance, the selection of the film and the ion exchange resin is the biggest difficult problem of industrial production, the stability of the film and the ion exchange resin for long-term use is poor, the reliability is low, the running cost is too high, and the practicability is poor.
Chinese patent CN103087348 neutralizes N-methylpyrrolidone-calcium chloride solvent with neutralizer to neutrality, then adds deionized water or reclaimed water to wash PPTA, carries out pressure distillation dehydration, and desalts the distilled slurry in a desalting kettle; finally, the desalted solvent is subjected to rectification, purification, recovery and recycling. The method comprises the steps of distilling the neutralized solvent to obtain water and trace NMP, then distilling and collecting NMP, removing a large amount of salt in the solvent after removing water, increasing the tar generated by NMP pyrolysis due to salt enrichment at the bottom in distillation, and simultaneously, causing the irrecoverable waste salt, so that the recycling period is short and continuous production is not realized, and increasing the energy consumption and the production cost due to direct distillation of a large amount of water in the solvent.
Chinese patent CN101457414 proposes a method for recovering solvent NMP in the production process of para-aramid: the method comprises the steps of extracting a solvent NMP used in the production process of para-aramid fiber by using aromatic haloalkane as an extracting agent, and recovering NMP in an extracting phase by distillation. The method is characterized in that the extraction and separation are directly carried out, so that incomplete removal of the extractant can be caused, and serious corrosion of equipment is easily caused by hydrolysis of the extractant under the high-temperature condition; the products of the hydrolysis of the extractant and impurities in the solution can accelerate the NMP cracking, so that NMP loss is caused, more impurities are mixed in the NMP during recovery, and the polycondensation reaction of the later polymerization and the synthesis of PPTA are affected; meanwhile, the extraction effect of the extracting agent which is not purified in the recycling process can be influenced.
Disclosure of Invention
The invention aims to provide a system which can improve the recovery rate and reduce the energy consumption in the production process of para-aramid fiber, and recycle nitrogen-methyl pyrrolidone (NMP) in a salt-containing organic solvent and hydrochloride in the solvent.
In order to achieve the above purpose, the invention designs a separation and recovery system of NMP in salt-containing solution, comprising an extraction device, a stripping tower, an extractant removing device, a crude NMP purifying device and a salt solution recovering device;
the extraction device comprises a mother liquor storage tank, a disk extraction tower, an extractant storage tank and an extraction intermediate tank; the output end of the mother liquor storage tank is communicated with the bottom of the disc type extraction tower through a pipeline, the output end of the extractant storage tank is communicated with the top of the disc type extraction tower through a pipeline, and the output end of the bottom of the disc type extraction tower is communicated with the extraction intermediate tank through a pipeline; the upper part of the disc type extraction tower is communicated with the upper part of the stripping tower through a pipeline;
the extractant removing device comprises an extractant removing feeding heater, an extractant removing tower reboiler, an extractant condenser and an extractant purifying storage tank; the output end of the extraction intermediate tank is communicated with an extractant removing feeding heater through a pipeline; the output end of the extractant removing feeding heater is communicated with the middle part of the extractant removing tower through a pipeline; the bottom end of the extractant removing tower is communicated with the input end of the reboiler of the extractant removing tower through a pipeline, and the output end of the reboiler of the extractant removing tower is communicated with the extractant removing tower through a pipeline; the output ends of the tops of the extractant removing tower and the stripping tower are communicated with an extractant condenser through pipelines; the output end of the extractant condenser is communicated with an extractant purifying storage tank through a pipeline; the output end of the extractant purifying storage tank is provided with three branches, wherein the first branch is communicated with the top of the extractant removing tower, the second branch is communicated with the extractant storage tank, and the third branch is communicated with the stripping tower;
the crude NMP purification device comprises an NMP recovery tower, an NMP recovery tower reboiler, an NMP recovery condenser, an NMP reflux tank, an NMP storage tank and a waste residue heater; the output end at the bottom of the extractant removing tower is communicated with the middle part of the NMP recovery tower through a pipeline; the output end of the bottom of the NMP recovery tower is provided with two branches, the first branch is communicated with the input end of the reboiler of the NMP recovery tower, and the second branch is communicated with the waste residue heater; the output end of the reboiler of the NMP recovery tower is communicated with the bottom of the NMP recovery tower; the output end at the top of the NMP recovery tower is communicated with an NMP recovery condenser through a pipeline; the output end of the NMP recovery condenser is provided with two branches, the first branch is communicated with the NMP reflux tank, and the second branch is connected with a vacuum system; the output end of the NMP reflux tank is provided with three branches, the first branch is communicated with the NMP storage tank, the second branch is communicated with the NMP recovery tower, and the third branch is communicated with the vacuum system;
the salt solution recovery device comprises a waste salt solution storage tank, a first-stage evaporator heating chamber, a second-stage forced evaporator heating chamber, an evaporation condenser, a resin water washing tank, a salt solution storage tank and a crystallization flaker; the bottom output end of the stripping tower is communicated with a waste salt solution storage tank through a pipeline; the waste salt solution storage tank is communicated with the middle part of the primary evaporator through a pipeline, two branches are arranged at the output end of the bottom of the primary evaporator, the first branch is communicated with the primary heating chamber, and the second branch is communicated with the salt solution storage tank; the top output end of the primary evaporator is communicated with an evaporation condenser through a pipeline, and the output end of the evaporation condenser is communicated with a resin washing tank through a pipeline; the output end of the bottom of the secondary forced evaporator is provided with two branches, wherein the first branch is communicated with the input end of the heating chamber of the secondary forced evaporator, and the second branch is connected with the crystallization flaker; the output end of the salt solution storage tank is communicated with the input end of the heating chamber of the secondary forced evaporator; the output ends of the bottoms of the first-stage evaporator heating chamber and the second-stage forced evaporator heating chamber are communicated with an evaporation condenser through pipelines; the output end of the top of the heating chamber of the primary evaporator is communicated with the middle part of the primary evaporator; the output end of the heating chamber top of the secondary forced evaporator is communicated with the secondary forced evaporator.
Further, a mother liquor pH meter is arranged on the mother liquor storage tank, a mother liquor conveying pump is arranged at the output end of the mother liquor storage tank, and a mother liquor flowmeter is arranged on a pipeline connecting the mother liquor storage tank and the disc type extraction tower; an extractant conveying pump is arranged at the output end of the extractant storage tank, and an extractant flowmeter is arranged on a pipeline connecting the extractant storage tank with the disk type extraction tower; an extraction flowmeter is arranged on a pipeline connecting the disk extraction tower and the extraction intermediate tank.
Further, an extraction intermediate delivery pump is arranged at the output end of the extraction intermediate tank, and an extraction phase flowmeter is arranged on a pipeline connected with the extraction agent removing and feeding heater.
Further, a salt solution delivery pump is arranged at the bottom output end of the stripping tower; the output end of the bottom of the extractant removing tower is provided with an extractant removing tower bottom pump.
Further, a pipeline connected with the extracting agent removing tower and the NMP recovery tower is provided with a NMP purification tower feeding flowmeter; an extractant conveying pump is arranged on the second branch of the output end of the extractant purifying storage tank, and an extractant removing tower bottom pump is arranged on the first branch of the output end of the extractant purifying storage tank.
Further, the output of NMP recovery tower is equipped with NMP recovery tower bottom pump, NMP reflux drum output is equipped with NMP reflux pump.
Further, the output end of the waste salt solution storage tank is provided with a waste salt conveying pump; the input end of the heating chamber of the secondary forced evaporator is provided with a forced circulation pump; the output end of the saline solution storage tank is provided with a saline solution delivery pump.
Compared with the prior art, the invention has the beneficial effects that:
1. the energy consumption is greatly reduced in the whole separation process. According to the invention, a rotary disk type extraction technology is adopted to convert NMP and water into NMP and chloroform, and the NMP and water are separated only by adopting electric loss according to the characteristics of materials in the whole separation process.
2. The salt content in NMP is less than or equal to 0.05% by separation of extraction technology, so that the periodic increase of intermittent system operation and cleaning caused by salt enrichment in the tower bottom in recovery rectification is solved; the reduction of the salt content solves a series of problems such as the influence of salt on NMP pyrolysis under the high temperature condition, thereby achieving long-period running of the system and increasing the recovery rate of NMP.
3. The tray type extraction tower can reduce the salt content in the extraction phase to less than or equal to 0.05%, reduce the NMP content in the raffinate phase to less than or equal to 0.05%, and ensure that the final recovery rate of NMP reaches more than 99.93%.
4. The raffinate phase is an aqueous solution of salt, NMP and extractant, wherein NMP is less than or equal to 0.05 percent, extractant is less than or equal to 0.12 percent, and stripping is adopted to remove the extractant to achieve that the extractant in the separated salt solution is less than or equal to 0.0001 percent; the salt solution without the extractant can be directly concentrated by first-stage evaporation to obtain 35% salt solution, the 35% salt solution is returned to the solvent preparation for refining, the solvent preparation is used as a cosolvent of a polymerization device, the redundant 35% salt solution enters a second-stage forced evaporator for further concentration, the salt solution with the salt content of 65% is achieved, and the concentrated 65% salt solution directly enters a flaking crystallizer; the heat source of the double-effect forced evaporator adopts medium-pressure steam used by the system, and a pipeline is not required to be paved; the raw steam generated by the two-effect forced evaporator can return to the first-stage evaporator to be used as a heat source of the first-stage evaporator, condensed water of the two groups of evaporators and distilled water of the first-stage evaporator are condensed by the condenser and return to the resin washing storage tank to be stored for resin washing; the two groups of evaporators are all operated by vacuum, and can be operated by using the existing vacuum pump without purchasing other vacuum equipment.
5. The extraction phase enters a rectifying tower (namely an extractant removing tower) to remove chloroform in the solution, and the residual trace chloroform is removed at the bottom in a steam stripping mode because trace chloroform is difficult to remove and has the characteristic of easy hydrolysis, meanwhile, the chloroform content in the crude NMP solvent is less than or equal to 0.0001 percent, the water content is controlled to be 5 to 7 percent, the corrosion of chloroform hydrolysis to equipment can be prevented, the requirement of NMP water in a polymerization ratio is met, and the use requirement is directly met without preparing NMP solution before compounding.
6. Because the solution contains trace salt and other impurities, the crude NMP solution is purified by adopting a decompression rectification mode, and the NMP solvent meets the direct use requirement.
Drawings
FIG. 1 is a schematic diagram of a system for separating and recovering NMP from a salt-containing solution according to the present invention.
Detailed Description
Further advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present invention, which is described by the following specific examples.
Example 1
As shown in fig. 1, a system for separating and recovering NMP in a salt-containing solution comprises an extraction device, a stripping tower 9, an extractant removing device, a crude NMP purifying device and a salt solution recovering device;
the extraction device comprises a mother liquor storage tank 1, a disk extraction tower 6, an extractant storage tank 3 and an extraction intermediate tank 7; the output end of the mother liquor storage tank 1 is communicated with the bottom of the disc type extraction tower 6 through a pipeline, the output end of the extractant storage tank 3 is communicated with the top of the disc type extraction tower 6 through a pipeline, and the output end of the bottom of the disc type extraction tower 6 is communicated with the extraction intermediate tank 7 through a pipeline; the upper part of the disk extraction tower 6 is communicated with the upper part of the stripping tower 9 through a pipeline; the bottom output end of the stripping tower 9 is provided with a salt solution delivery pump 10;
a mother liquor pH meter 2 is arranged on the mother liquor storage tank 1, a mother liquor delivery pump 4 is arranged at the output end of the mother liquor storage tank 1, and a mother liquor flowmeter 26 is arranged on a pipeline connected with the tray type extraction tower 6 of the mother liquor storage tank 1; an extractant delivery pump 5 is arranged at the output end of the extractant storage tank 3, and an extractant flowmeter 27 is arranged on a pipeline connecting the extractant storage tank 3 with the disk type extraction tower 6; an extraction flowmeter 28 is arranged on a pipeline connecting the disk extraction tower 6 and the extraction intermediate tank 7;
the extractant removing device comprises an extractant removing feed heater 11, an extractant removing column 12, an extractant removing column reboiler 14, an extractant condenser 15 and an extractant purifying storage tank 16; the output end of the extraction intermediate tank 7 is communicated with an extractant removing feed heater 11 through a pipeline, an extraction intermediate delivery pump 8 is arranged at the output end of the extraction intermediate tank 7, and an extraction phase flowmeter 29 is arranged on the pipeline connecting the extraction intermediate tank 7 and the extractant removing feed heater 11; the output end of the extractant removing feeding heater 11 is communicated with the middle part of the extractant removing tower 12 through a pipeline; the bottom end of the extractant removing tower 12 is communicated with the input end of the extractant removing tower reboiler 14 through a pipeline, and the output end of the extractant removing tower reboiler 14 is communicated with the extractant removing tower 12 through a pipeline; the output ends of the tops of the extractant removing tower 12 and the stripping tower 9 are communicated with an extractant condenser 15 through pipelines; the output end of the extractant condenser 15 is communicated with an extractant purifying storage tank 16 through a pipeline; the output end of the extractant purifying storage tank 16 is provided with three branches, wherein the first branch is communicated with the top of the extractant removing tower 12, the second branch is communicated with the extractant storage tank 3, and the third branch is communicated with the stripping tower 9;
an extractant conveying pump 17 is arranged on the second branch of the output end of the extractant purifying storage tank 16, and an extractant removing tower bottom pump 18 is arranged on the first branch of the output end of the extractant purifying storage tank 16; the crude NMP purification device comprises an NMP recovery tower 19, an NMP recovery tower reboiler 21, an NMP recovery condenser 22, an NMP reflux tank 23, an NMP storage tank 45 and a waste residue heater 25; the output end at the bottom of the extractant removing tower 12 is communicated with the middle part of the NMP recovery tower 19 through a pipeline, and the output end at the bottom of the extractant removing tower 12 is provided with an extractant removing tower bottom pump 13; the pipeline of the extractant removing tower 12 connected with the NMP recovery tower 19 is provided with an NMP purification tower feeding flowmeter 30; the output end at the bottom of the NMP recovery tower 19 is provided with two branches, the first branch is communicated with the input end of the NMP recovery tower reboiler 21, and the second branch is communicated with the waste residue heater 25; the output end of the NMP recovery tower reboiler 21 is communicated with the bottom of the NMP recovery tower 19; the top output end of the NMP recovery tower 19 is communicated with an NMP recovery condenser 22 through a pipeline; the output end of the NMP recovery condenser 22 is provided with two branches, the first branch is communicated with the NMP reflux tank 23, and the second branch is connected with a vacuum system 46; the output end of the NMP reflux tank 23 is provided with three branches, the first branch is communicated with an NMP storage tank 45, the second branch is communicated with an NMP recovery tower 19, and the third branch is communicated with a vacuum system 46;
the output end of the NMP recovery tower 19 is provided with an NMP recovery tower bottom pump 20, and the output end of the NMP reflux tank 23 is provided with an NMP reflux pump 24;
the brine recovery device comprises a waste brine storage tank 31, a first-stage evaporator 33, a first-stage evaporator heating chamber 34, a second-stage forced evaporator 36, a second-stage forced evaporator heating chamber 37, an evaporation condenser 35, a resin water washing tank 42, a brine storage tank 40 and a crystallization flaker 39; the bottom output end of the stripping tower 9 is communicated with a waste salt solution storage tank 31 through a pipeline; the waste salt solution storage tank 31 is communicated with the middle part of the primary evaporator 33 through a pipeline, two branches are arranged at the bottom output end of the primary evaporator 33, wherein the first branch is communicated with the primary heating chamber 34, and the second branch is communicated with the salt solution storage tank 40; the top output end of the primary evaporator 33 is communicated with the evaporative condenser 35 through a pipeline, the output end of the evaporative condenser 35 is provided with two branches, the first branch is communicated with the resin washing tank 42, and the second branch is communicated with the condenser vacuum system 47; the bottom output end of the secondary forced evaporator 36 is provided with two branches, wherein the first branch is communicated with the input end of the heating chamber 37 of the secondary forced evaporator, and the second branch is connected with the crystallization flaker 39; the output end of the salt solution storage tank 40 is communicated with the input end of the heating chamber 37 of the secondary forced evaporator (in order to facilitate the refining of the salt solution discharged from the salt solution storage tank 40, the output end of the salt solution storage tank 40 can be also provided with a second branch connected with a subsequent refined solvent preparation unit); the bottom output ends of the first-stage evaporator heating chamber 34 and the second-stage forced evaporator heating chamber 37 are communicated with the evaporation condenser 35 through pipelines; the output end of the top of the first-stage evaporator heating chamber 34 is communicated with the middle part of the first-stage evaporator 33; the output end of the top of the heating chamber 37 of the secondary forced evaporator is communicated with the secondary forced evaporator 36;
the output end of the waste salt solution storage tank 31 is provided with a waste salt delivery pump 32; the input end of the heating chamber 37 of the secondary forced evaporator is provided with a forced circulation pump 38; the output end of the saline solution storage tank 40 is provided with a saline solution feeding pump 41.
The process method of the NMP separation and recovery system in the salt-containing solution comprises the following steps: the chloroform is used as an extractant, NMP in a salt solution is extracted in the production process, the NMP is positioned in an extraction phase, the extractant in the extraction phase is recovered through rectification for recycling, and the NMP is purified and directly used in polymerization production. The method comprises the following specific steps:
1. washing synthetic PPTA resin with water to obtain a solvent consisting of 52% of water, 42% of NMP, 6% of salt and trace oligomers, storing the solvent in a mother liquor storage tank 1 to be used as mother liquor, regulating the pH of the mother liquor to 7-8 by using a mother liquor pH meter 2, filtering the oligomers and impurities in the solvent, conveying the solvent to the bottom of a tray type extraction tower 6 through the regulation of a mother liquor conveying pump 4 and a mother liquor flowmeter 26, conveying an extractant in an extractant storage tank 3 to the top of the tray type extraction tower 6 for extraction separation through the regulation of an extractant conveying pump 5 and an extractant flowmeter 27, conveying an extract phase at the bottom of the tray type extraction tower 6 to an extraction intermediate tank 7 after being metered by an extraction flowmeter 28, and conveying the extract phase in the extraction intermediate tank 7 to an extractant removal feed heater 11 after being metered by an extraction intermediate conveying pump 8 and an extraction phase flowmeter 29;
2. the stripping step is as follows: the trace chloroform in the raffinate phase is condensed and recovered by adopting a stripping mode, so that the discharge of dangerous chemicals is prevented, the extractant chloroform in the extractant storage tank 3 and the solvent neutralized by the mother liquor storage tank 1 enter a disk extraction tower 6 according to the mass ratio of 4:1, and NMP in the solvent in the disk extraction tower 6 is transferred to chloroform to form an extraction phase; the brine solution and trace chloroform form a raffinate phase, the raffinate phase at the top of the tray type extraction tower 6 is conveyed to a stripping tower 9 to remove residual chloroform in the raffinate phase, the gas phase distilled out of the top of the stripping tower 9 is conveyed to an extractant condenser 15 for condensation separation, and the salt solution at the bottom of the stripping tower 9 is conveyed to a waste salt solution storage tank 31 through a salt solution conveying pump 10;
3. the extraction agent removal step is: the extraction phase is heated to the bubble point temperature in an extractant removing feed heater 11, then enters an extractant removing tower 12, and is separated in a normal pressure rectification mode; the material at the bottom of the extractant removing tower 12 is conveyed to an extractant removing tower reboiler 14 through an extractant removing tower bottom pump 13 to be used as a heat source of the extractant removing tower 12, a steam input end is arranged at the bottom of the extractant removing tower 12, and trace steam is input at the bottom of the extractant removing tower 12 to carry out steam stripping to remove residual extractant; the bottom of the extractant removing tower 12 adopts a small amount of steam stripping mode to remove trace residual extractant in the solution, thereby preventing the damage of the extractant cracking to equipment and increasing the loss of NMP at high temperature; the extractant at the top end of the extractant removing tower 12 and the gas phase output from the top end of the stripping tower 9 enter an extractant condenser 15 together in a gas phase form for condensation and separation; after condensation and separation, the residual extractant is purified by an extractant purifying storage tank 16, and then is conveyed to an extractant storage tank 3 for recycling by an extractant conveying pump 17, a water phase is conveyed to an extractant removing column 12 in a reflux way by a water phase conveying pump 18, stable operation is ensured, excessive water enters a stripping column 9, the residual extractant in the water phase is recycled again to prevent external discharge, and crude NMP solvent at the bottom of the extractant removing column 12 is conveyed to an NMP recovery column 19 by an extractant removing column bottom pump 13 and an NMP purifying column feeding flowmeter 30;
4. the steps of crude NMP purification are: the NMP subjected to extractant removal is a crude NMP solvent, the crude NMP is conveyed to an NMP recovery tower reboiler 21 through an NMP recovery tower bottom pump 20 to provide a heat source for an NMP recovery tower 19, impurities in the crude NMP solvent are removed in the NMP recovery tower 19 in a decompression rectification mode, pure NMP distilled out of the NMP recovery tower 19 is condensed through an NMP recovery tower top condenser 22 and then enters an NMP recovery tower reflux tank 23, part of NMP in the output end of the NMP recovery tower reflux tank 23 is refluxed to the NMP recovery tower 19, the stable operation of the NMP recovery tower 19 is ensured, and the other part of NMP is conveyed to an NMP storage tank 45; after the residual tar and other heavy component materials are conveyed to a waste residue heater 25 for heating through an NMP recovery tower bottom pump 20, the residual tar is discharged and recovered in a timed and quantitative mode through a subsequent tar recovery system, the heavy components in the waste salt solution are prevented from affecting the quality of later recovered salt, and a purified NMP solution is obtained through a crude NMP purification device;
5. the salt solution recovery step is as follows: the salt solution at the bottom of the stripping tower 9 is conveyed to a waste salt solution storage tank 31 through a salt solution conveying pump 10, the residual salt solution is pre-concentrated by adopting a single-effect evaporator, waste salt in the waste salt solution storage tank 31 is conveyed to a first-stage evaporator 33 through a waste salt conveying pump 32, the waste salt is concentrated into 35% salt solution through a first-stage evaporator heating chamber 34, steam at the top of the first-stage evaporator 33 is condensed and recycled to a resin water-washing tank 42 through an evaporation condenser 35 for resin water washing, the 35% salt solution in the first-stage evaporator heating chamber 34 is conveyed to a salt solution storage tank 40, a part of the salt solution is conveyed to a refined solvent preparation unit through a salt solution conveying pump 41 for batching, the other part of the salt solution is conveyed to a second-effect forced evaporator heating chamber 37 through a forced circulation pump 38 for evaporation concentration, the salt solution with the concentration of 65%, the heat source of the second-stage forced evaporator heating chamber 37 is medium-pressure steam used by the system, the steam generated by the second-stage forced evaporator heating chamber 37 enters the first-stage evaporator heating chamber 34 as the heat source, the salt solution after the concentration of the second-effect forced evaporator 36 enters the crystallization crystallizer 39 for crystallization and is packaged after the crystallization and the crystallization, and the condensate water-washing tank 42 is filled into the resin water-washing tank 42 for recycling.
According to the recovery system, the salt content in NMP is less than or equal to 0.05%, so that the periodic increase of intermittent system operation and cleaning caused by salt enrichment in a tower kettle in recovery rectification is solved; the reduction of the salt content solves a series of problems such as the influence of salt on NMP pyrolysis under the high temperature condition, thereby achieving long-period operation of the system and increasing the recovery rate of NMP; the tray type extraction tower can reduce the salt content in the extraction phase to less than or equal to 0.05%, reduce the NMP content in the raffinate phase to less than or equal to 0.05%, and ensure that the final recovery rate of NMP reaches more than 99.93%; the raffinate phase is an aqueous solution of salt, NMP and extractant, wherein NMP is less than or equal to 0.05 percent, extractant is less than or equal to 0.12 percent, and stripping is adopted to remove the extractant to achieve that the extractant in the separated salt solution is less than or equal to 0.0001 percent; the rectifying tower (namely the extractant removing tower 12) removes residual trace chloroform at the bottom by a steam stripping mode, meanwhile, the chloroform content in the crude NMP solvent is less than or equal to 0.0001 percent, and the water content is controlled to be 5 to 7 percent, so that the corrosion of chloroform hydrolysis to equipment can be prevented.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (5)
1. The system for separating and recovering NMP in the salt-containing solution is characterized by comprising an extraction device, a stripping tower, an extractant removing device, a crude NMP purifying device and a salt solution recovering device;
the extraction device comprises a mother liquor storage tank, a disk extraction tower, an extractant storage tank and an extraction intermediate tank; the output end of the mother liquor storage tank is communicated with the disc type extraction tower through a pipeline, the output end of the extractant storage tank is communicated with the disc type extraction tower through a pipeline, and the output end of the bottom of the disc type extraction tower is communicated with the extraction intermediate tank through a pipeline; the upper part of the disc type extraction tower is communicated with the upper part of the stripping tower through a pipeline;
the extractant removing device comprises an extractant removing feeding heater, an extractant removing tower reboiler, an extractant condenser and an extractant purifying storage tank; the output end of the extraction intermediate tank is communicated with an extractant removing feeding heater through a pipeline; the output end of the extractant removing feeding heater is communicated with an extractant removing tower through a pipeline; the bottom end of the extractant removing tower is communicated with the input end of the reboiler of the extractant removing tower through a pipeline, and the output end of the reboiler of the extractant removing tower is communicated with the extractant removing tower through a pipeline; the output ends of the top of the extractant removing tower and the top of the stripping tower are communicated with an extractant condenser through pipelines; the output end of the extractant condenser is communicated with an extractant purifying storage tank through a pipeline; the output end of the extractant purifying storage tank is provided with three branches, wherein the first branch is communicated with the top of the extractant removing tower, the second branch is communicated with the extractant storage tank, and the third branch is communicated with the stripping tower;
the crude NMP purification device comprises an NMP recovery tower, an NMP recovery tower reboiler, an NMP recovery condenser, an NMP reflux tank, an NMP storage tank and a waste residue heater; the output end at the bottom of the extractant removing tower is communicated with an NMP recovery tower through a pipeline; the output end of the bottom of the NMP recovery tower is provided with two branches, the first branch is communicated with the input end of the reboiler of the NMP recovery tower, and the second branch is communicated with the waste residue heater; the output end of the reboiler of the NMP recovery tower is communicated with the NMP recovery tower; the output end at the top of the NMP recovery tower is communicated with an NMP recovery condenser through a pipeline; the output end of the NMP recovery condenser is provided with two branches, the first branch is communicated with the NMP reflux tank, and the second branch is connected with a vacuum system; the output end of the NMP reflux tank is provided with three branches, the first branch is communicated with the NMP storage tank, the second branch is communicated with the NMP recovery tower, and the third branch is communicated with the vacuum system;
the salt solution recovery device comprises a waste salt solution storage tank, a first-stage evaporator heating chamber, a second-stage forced evaporator heating chamber, an evaporation condenser, a resin water washing tank, a salt solution storage tank and a crystallization flaker; the bottom output end of the stripping tower is communicated with a waste salt solution storage tank through a pipeline; the waste salt solution storage tank is communicated with the primary evaporator through a pipeline, two branches are arranged at the bottom output end of the primary evaporator, wherein the first branch is communicated with the primary heating chamber, and the second branch is communicated with the salt solution storage tank; the top output end of the primary evaporator is communicated with an evaporation condenser through a pipeline, and the output end of the evaporation condenser is communicated with a resin washing tank through a pipeline; the output end of the bottom of the secondary forced evaporator is provided with two branches, wherein the first branch is communicated with the input end of the heating chamber of the secondary forced evaporator, and the second branch is connected with the crystallization flaker; the output end of the salt solution storage tank is communicated with the input end of the heating chamber of the secondary forced evaporator; the output ends of the bottoms of the first-stage evaporator heating chamber and the second-stage forced evaporator heating chamber are communicated with an evaporation condenser through pipelines; the output end of the top of the heating chamber of the primary evaporator is communicated with the primary evaporator; the output end of the top of the heating chamber of the secondary forced evaporator is communicated with the secondary forced evaporator;
a mother liquor pH meter is arranged on the mother liquor storage tank, a mother liquor delivery pump is arranged at the output end of the mother liquor storage tank, and a mother liquor flowmeter is arranged on a pipeline connecting the mother liquor storage tank and the disk extraction tower; an extractant conveying pump is arranged at the output end of the extractant storage tank, and an extractant flowmeter is arranged on a pipeline connecting the extractant storage tank with the disk type extraction tower; an extraction flowmeter is arranged on a pipeline connecting the disc type extraction tower and the extraction intermediate tank;
a pipeline connected with the extracting agent removing tower and the NMP recovery tower is provided with a NMP purification tower feeding flowmeter; an extractant conveying pump is arranged on the second branch of the output end of the extractant purifying storage tank, and an extractant removing tower bottom pump is arranged on the first branch of the output end of the extractant purifying storage tank.
2. The system for separating and recovering NMP from a salt-containing solution according to claim 1, wherein the output end of the extraction intermediate tank is provided with an extraction intermediate transfer pump, and an extraction phase flowmeter is provided on a pipeline connecting the extraction intermediate tank and the extractant removal feed heater.
3. The system for separating and recovering NMP from a salt-containing solution according to claim 1, wherein the bottom output end of the stripping tower is provided with a salt solution delivery pump; the output end of the bottom of the extractant removing tower is provided with an extractant removing tower bottom pump.
4. The system for separating and recovering NMP from a salt-containing solution according to claim 1, wherein the output end of the NMP recovery tower is provided with an NMP recovery tower bottom pump, and the output end of the NMP reflux tank is provided with an NMP reflux pump.
5. The system for separating and recovering NMP from a salt-containing solution according to claim 1, wherein the output end of the waste salt solution storage tank is provided with a waste salt delivery pump; the input end of the heating chamber of the secondary forced evaporator is provided with a forced circulation pump; the output end of the saline solution storage tank is provided with a saline solution delivery pump.
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| CN111995130B (en) * | 2019-10-24 | 2022-10-14 | 中化环境科技工程有限公司 | Treatment method for solvent recovery sewage generated in aramid fiber production process |
| CN111072053B (en) * | 2019-11-13 | 2022-09-09 | 中化高性能纤维材料有限公司 | Method for treating raffinate in recovery process of para-aramid solvent |
| CN111807593B (en) * | 2020-07-23 | 2023-07-18 | 河南神马芳纶技术开发有限公司 | Salt-containing organic wastewater treatment and utilization integrated device and process for para-aramid solvent working section |
| CN112933631A (en) * | 2021-02-02 | 2021-06-11 | 常州冀德环保科技有限公司 | Five-tower four-effect rectification system and recovery method for NMP waste liquid |
| CN112807732A (en) * | 2021-02-02 | 2021-05-18 | 常州冀德环保科技有限公司 | Three-tower two-effect rectification system and recovery method for NMP waste liquid |
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