CN109134339A - Method for recovering solvents is used in a kind of production of para-aramid fiber - Google Patents
Method for recovering solvents is used in a kind of production of para-aramid fiber Download PDFInfo
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- CN109134339A CN109134339A CN201811066893.4A CN201811066893A CN109134339A CN 109134339 A CN109134339 A CN 109134339A CN 201811066893 A CN201811066893 A CN 201811066893A CN 109134339 A CN109134339 A CN 109134339A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D207/00—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom
- C07D207/02—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D207/18—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member
- C07D207/22—Heterocyclic compounds containing five-membered rings not condensed with other rings, with one nitrogen atom as the only ring hetero atom with only hydrogen or carbon atoms directly attached to the ring nitrogen atom having one double bond between ring members or between a ring member and a non-ring member with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D207/24—Oxygen or sulfur atoms
- C07D207/26—2-Pyrrolidones
- C07D207/263—2-Pyrrolidones with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms
- C07D207/267—2-Pyrrolidones with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to other ring carbon atoms with only hydrogen atoms or radicals containing only hydrogen and carbon atoms directly attached to the ring nitrogen atom
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Abstract
The present invention relates to a kind of para-aramid fiber production method for recovering solvents, belong to field of fine chemical.The hydrochloric acid that in calcium carbonate and polymerization generates is added into the cleaning solution after PPTA polymerization first, cleaning solution after neutralization is transported in extraction tower and carries out extraction and separation, extraction phase is transported to rough sorting device extraction agent and NMP obtains rough segmentation material, rough segmentation material addition hot water is sent to the further extraction agent of smart separating device and obtains essence and divides material, essence divides material to be sent in purification evaporator after progress NMP purification and recovery, rectifying waste liquid is subjected to ion exchange and precipitation process, it is press-filtered out after sediment and filtrate is re-delivered to extraction tower progress extraction and separation, NMP is transported to paradigmatic system and prepares p-phenylenediamine solution after mixing and cool down with calcium chloride water.The method of the present invention efficiently solves the problems, such as that acidification problem is decomposed in the processing of rectifying waste liquid and extractant, improves the NMP rate of recovery and recycling quality, and does not influence solvent recovery production steady and continuous operation.
Description
Technical field
The present invention relates to a kind of para-aramid fiber production method for recovering solvents, belong to field of fine chemical.
Background technique
Para-aramid fiber is a kind of important high molecular material, is had extensively in aerospace, national defence and numerous civil fields
General application.The production of para-aramid fiber is generally divided into three parts: polymerization, solvent recovery and spinning.Wherein polymerization is by list
Body p-phenylenediamine and paraphthaloyl chloride are in solvent N-methyl pyrilidone (NMP)/cosolvent calcium chloride (CaCl2) low in system
Warm solution polycondensation is then washed with water at fluoropolymer resin (PPTA) by NMP, CaCl2, by-product hydrochloric acid and micro oligomer with
PPTA separation, respectively becomes pure polymer powder and cleaning solution；Solvent recovery is first by hydrochloric acid neutralisation treatment in cleaning solution
At salt, then solvent NMP is separated with suitable mode from cleaning solution, NMP is then re-used as solvent and enters polymerization
System.Since solvent NMP is continuously recycled, NMP quality can make a significant impact polymerization, and then influence spinning effect and fibre
Performance is tieed up, therefore the recovering effect of solvent NMP is extremely important, purity and the rate of recovery including recycling.
Currently used solvent recovery technology has direct rectification method and extraction fractional distillation.Wherein extraction fractional distillation is because of NMP
The rate of recovery is high and becomes main recovery method.Extraction fractional distillation is to make extractant from cleaning solution with low boiling point chloralkane to extract
NMP is taken out, then rectifying extraction agent and NMP again.But there are problems that two in separation distillation process: first is that extractant
There are acidification phenomenons for chloralkane.Chloralkane is heated to be easy to slough chlorine atom generation hydrogen chloride.And in point of extractant and NMP
From needing to heat in the process, and as the reduction separation temperature of extraction agent content can higher and higher, thus chloralkane in the presence of by
The risk of thermal decomposition, especially under conditions of temperature higher (≤120 DEG C).Chloralkane decomposes the hydrogen chloride generated and not only corrodes
Equipment, and (hydrogen chloride and NMP have stronger intermolecular force) can also improve the acidity of NMP in entrance NMP, and then influence
Solubility and PPTA polymerization speed of the subsequent calcium chloride in NMP, it is final to influence polymerization stability and polymerization effect；Second is that smart
Evaporate the processing problem of waste liquid.Chloralkane can extract together a small amount of cosolvent calcium chloride and oligomer during extracting NMP
Into extraction phase, these impurity can be accumulated gradually during later separation extractant and purification NMP.Because calcium chloride and
NMP has strong Complex effect, and calcium chloride and NMP can become because of Complex effect when NMP content is 25% or so
Solid, along with factors such as oligomer thickeninies, distillation column bottom liquid cognition gradually becomes the sticky liquid of brown or black, referred to as
Rectifying waste liquid.Rectifying waste liquid can be deposited in the reboiler of bottom since density is bigger, and the characteristic of the viscous saliferous of height can not only reduce
Reboiler heat transfer efficiency, and complicated etching problem can be generated.Therefore, for extracting rectifying remanufacture being capable of steady and continuous
Operation, it is necessary to solve the problems, such as two above.
It is acidified problem for chloralkane extractant, auxiliary agent is added to inhibit chloralkane to decompose or absorb its decomposition product
It is one of technical solution.Chloroform does with the amine of low molecular weight (such as triethylamine) in patent US4980031 in E.I.Du Pont Company
The absorbent of decomposition product hydrogen chloride.The acidification rate of recovery system can be effectively reduced by absorbing hydrogen chloride for these amines,
But since these aminated compounds boiling points are lower, separation process can be complicated during separating chloroform and purifying NMP.
ZL201510756359.6 inhibits the decomposition of chloralkane by the way that higher boiling phenols or alcohol compound is added, but these chemical combination
Price lattice are higher, and there is also spoilage problems in long-term thermal histories.
Report is disclosed at present seldom for the solution of direct rectifying waste liquid.ZL201410384495.2 directly distillation
Mode recycle NMP.The phase impacts distillation to reduce kettle liquid viscosity after distillation, and proposition is dropped with the mode of rotary drum desalination
Low evaporation residue viscosity.But the solid slag of this method abjection is mainly calcium chloride and NMP complex compound.Because calcium chloride and
NMP strong Complex effect, NMP content is 20% or more in solid slag.Therefore this processing mode one to lose more
NMP, two this solid slags are difficult to handle, and become liquid again quickly after natural storage water suction, there is the risk of pollution environment.
Summary of the invention
The purpose of the present invention is the shortcomings to overcome prior art, propose a kind of para-aramid fiber production solvent
Recovery method.The method of the present invention had both efficiently solved the problems, such as that acidification problem was decomposed in the processing of rectifying waste liquid and extractant, also improved
The NMP rate of recovery and recycling quality, and do not influence solvent recovery production steady and continuous operation.
The present invention proposes a kind of para-aramid fiber production method for recovering solvents, comprising the following steps:
(1) hydrochloric acid that in calcium carbonate and polymerization generates is added into the cleaning solution after PPTA polymerization, reaches cleaning solution pH value
To between 5-7；Cleaning solution after neutralization is transported in extraction tower and carries out extraction and separation, the extractant used be methylene chloride or
Chloroform；Overhead extraction raffinate phase is extracted, tower bottom produces extraction phase；By extraction phase be transported to rough sorting device carry out extractant and
The separation of NMP goes raffinate phase conveying to carry out wastewater treatment；
(2) rough sorting device is using thin film evaporator or destilling tower and its ancillary equipment, under the conditions of decompression and heating evaporation,
Extractant is removed from extraction phase；Rough sorting device keeps operation temperature between 50-90 DEG C, and vacuum degree is maintained at -0.05~-
Between 0.09MPa, extractant is produced at the top of rough sorting device, rough sorting device bottom produces rough segmentation material, extractant in rough segmentation material
Content is maintained between 10-20%；
(3) rough segmentation material addition hot water is sent to the further extraction agent of smart separating device together；Smart separating device is using essence
Evaporate tower；Hot water additive amount is the 2-10% of rough segmentation material, and hot water temperature is at 50-90 DEG C；The reboiler temperature control of rectifying column exists
100-110 DEG C, the control of overhead reflux temperature at 50-70 DEG C, the top of the distillation column vacuum degree be maintained at -0.095~-0.098MPa it
Between；Extraction includes extractant, water and NMP at the top of rectifying column, continuously produces essence in the reboiler at rectifying column bottom and divides material, essence divides object
Agent content control is extracted in material between 0.05-0.2%；
(4) material will be divided to be transported in purification evaporator from the essence continuously produced in the reboiler at rectifying column bottom and carries out NMP
Purification and recovery；Purification evaporator is scraper-type evaporator, and heating outside evaporator makes temperature in evaporator be maintained at 100-110
Between DEG C, vacuum degree is maintained between -0.095~-0.098MPa；NMP is produced at the top of evaporator, rectifying is discharged in base of evaporator
Waste liquid, the every 12h discharge of rectifying waste liquid are primary；
(5) rectifying waste liquid is transported in settler, flocculant is first added under agitation, is added after 5-10min
Salt or aqueous alkali carry out ion exchange and further precipitation process, the solution being disposed to rectifying waste liquid；Flocculation
Agent is anion or non-ionic polyacrylamide；Flocculant addition is the 1-5% of rectifying waste liquid, and when use is molten by flocculant
Solution is made into the aqueous solution of concentration 0.1-1% in water；The additional amount of salt or alkali is subject to entire reaction system and no longer generates precipitating；
Wherein salt includes sodium carbonate and potassium carbonate；Alkali includes sodium hydroxide and potassium hydroxide；Salt or alkali concentration control are in 1-5%；
(6) solution of step (5) being disposed is press-filtered out sediment, the filtrate that filter press extrudes with plate and frame filter press
Cleaning solution mixing after returning to step (1) and neutralizing, and be transported to extraction tower and carry out extraction and separation, what filter press extruded
Sediment is as fixed-end forces；
(7) NMP that step (4) obtains is mixed with concentration 30-50% calcium chloride water, then carries out rectifying and dewatering,
The NMP/ calcium chloride solution that moisture content is lower than 100ppm is obtained, dehydration afterchlorinate calcium concentration is stably held between 6-8%, by this
Paradigmatic system is transported to after solution is cooling and prepares p-phenylenediamine solution, starts to carry out secondary cycle use.
The characteristics of the method for the present invention and beneficial effect are:
The present invention decomposes acidification problem for extractant chloralkane, reduces rectifying column operation with the steam stripped method of heating water
Temperature, and then chloralkane decomposition rate is reduced, save the trouble of addition stabilizer or acid absorbent；For rectifying liquid waste processing
Problem removes oligomer therein with flocculant, is imitated with the complexing that other metal ions replace calcium ion to eliminate calcium chloride and NMP
It answers, and then reduces the viscosity and impurity content of rectifying waste liquid.Then by treated, waste liquid return extraction tower continues to extract
Distillation process.
Distillation operation temperature is reduced with vaporizing extract process when rectifying removes extractant, extractant is not only effectively reduced and decomposes wind
Danger, and it is little in this stage stripping amount of water, waste water system can be entered in reextraction into the water in chloroform, entered
Aqueous in NMP can add dehydration of salt section to remove, and this method does not both need to increase extras and auxiliary agent, nor affects on solvent
The stable operation of recycling；Not only method is simple for flocculation and ion exchange processing rectifying waste liquid, but also can effectively improve NMP recycling
Rate does not influence solvent recovery production steady and continuous operation while guaranteeing the quality of NMP of recycling.
Detailed description of the invention
Fig. 1 is the flow diagram of the method for the present invention.
Specific embodiment
The present invention proposes a kind of para-aramid fiber production method for recovering solvents, in the following with reference to the drawings and specific embodiments
It is further described as follows.
The present invention proposes a kind of para-aramid fiber production method for recovering solvents, overall flow as shown in Figure 1, include with
Lower step:
(1) it extracts: the hydrochloric acid that in calcium carbonate and polymerization generates being added into the cleaning solution after PPTA polymerization, makes cleaning solution pH
Value reaches between 5-7.Cleaning solution after neutralization is transported in extraction tower and carries out extraction and separation.The extractant used is dichloromethane
Alkane or chloroform；Overhead extraction raffinate phase is extracted, tower bottom produces extraction phase；Extraction phase is transported to rough sorting device to extract
The separation of agent and NMP goes raffinate phase conveying to carry out wastewater treatment；
(2) rough segmentation: rough sorting device is using thin film evaporator or destilling tower and its ancillary equipment, in decompression and heating evaporation item
Under part, most of extractant is removed from extraction phase；In order to avoid the acidification of extractant, rough sorting device keeps operation temperature to exist
Between 50-90 DEG C, vacuum degree is maintained between -0.05~-0.09MPa.Extractant is produced at the top of rough sorting device and is returned again
To the extraction stages of step (1).Rough sorting device bottom produces rough segmentation material, and rough segmentation material includes including NMP, extractant and miscellaneous
Matter；Agent content will be extracted in rough segmentation material by control inlet amount to be maintained between 10-20%；
(3) rough segmentation material addition hot water rectifying: is sent to the further extraction agent of smart separating device together；Smart separating device is adopted
Use rectifying column；(water reduces the operation temperature of rectifying column simultaneously into the vaporization that can be heated after tower, using the stripping effect of the vapor of vaporization
Accelerate the separation of extractant and NMP.) hot water additive amount be rough segmentation material 2-10%, hot water temperature is at 50-90 DEG C；Rectifying column
Reboiler temperature control at 100-110 DEG C, overhead reflux temperature is controlled at 50-70 DEG C.The top of the distillation column vacuum degree is maintained at-
Between 0.095~-0.098MPa；What is produced at the top of rectifying column is mainly that (extractant also comes back to step (1) to extractant
Extraction stages), remaining group is divided into water and NMP；Essence is continuously produced in the reboiler at rectifying column bottom and divides material, by controlling rectifying column
Essence is divided in material and extracts agent content control between 0.05-0.2% by parameter and produced quantity；
(4) refine: by from the essence continuously produced in the reboiler at rectifying column bottom divide material be transported to purification evaporator in into
Row NMP purification and recovery；Purification evaporator is scraper-type evaporator, and heating outside evaporator is maintained at temperature in evaporator
Between 100-110 DEG C, vacuum degree is maintained between -0.095~-0.098MPa；NMP is produced at the top of evaporator, rectifying waste liquid
It is discharged from base of evaporator, main chloride containing calcium, NMP, oligomer, water and microextraction agent in rectifying waste liquid；Rectifying waste liquid is every
12h discharge is primary；
(5) it flocculates: rectifying waste liquid is transported in settler；Flocculation is first added under agitation in settler
Salt or aqueous alkali are added after 5-10min and carries out ion exchange and further precipitation process to rectifying waste liquid, is handled for agent
The solution finished；Flocculant is anion or non-ionic polyacrylamide；Flocculant addition is the 1-5% of rectifying waste liquid,
Flocculant is dissolved in water to the aqueous solution for being made into concentration 0.1-1% when use；The additional amount of salt or alkali is with entire reaction system
No longer generate subject to precipitating.Wherein salt includes sodium carbonate and potassium carbonate；Alkali includes sodium hydroxide and potassium hydroxide.Salt or alkali concentration
Control is in 1-5%；The salt or aqueous alkali of addition can be reacted with calcium chloride generates winnofil or calcium hydroxide, molten in this way
Existing leading ion is non-calcium ion (sodium or potassium ion) in liquid system, these ions and the not strong Complex effect of NMP, this
The viscosity and Complex effect of waste liquid can be effectively reduced in sample；
(6) it is dehydrated: the solution of step (5) being disposed being press-filtered out sediment with plate and frame filter press, filter press extrudes
Filtrate return to step (1) and neutralize after cleaning solution mixing, and be transported to extraction tower, then carry out extraction essence again
The processes such as evaporate.The sediment that filter press extrudes is as fixed-end forces；
(7) NMP that step (4) obtains is mixed with concentration 30-50% calcium chloride water, then carries out rectifying and dewatering,
Obtain the NMP/ calcium chloride solution that moisture content is lower than 100ppm.Dehydration afterchlorinate calcium concentration is stably held between 6-8%.It should
Paradigmatic system is transported to after solution is cooling and prepares p-phenylenediamine solution, starts to carry out secondary cycle use.
Below by embodiment, invention is further explained, but content not thereby limiting the invention.
Embodiment 1:
Cleaning solution after being polymerize PPTA with calcium carbonate, which is neutralized to pH, reaches 6 or so.Then the cleaning solution after neutralization is defeated
It is sent in extraction tower and carries out extraction and separation, extractant is chloroform.Extraction tower bottom extraction extraction phase is sent to rough segmentation workshop section and is extracted
Take agent and the separation of NMP.The main equipment of rough segmentation is two falling film evaporators.Level-one evaporator keeps operation temperature on 60 DEG C of left sides
The right side, vacuum degree are maintained at -0.06MPa or so.Secondary evaporimeter keeps operation temperature at 80 DEG C or so, and vacuum degree is maintained at-
0.07MPa or so.Chloroform extraction at the top of two evaporators, bottom produce rough segmentation material.Agent content is extracted in rough segmentation material to exist
10% or so；Rough segmentation material is sent to the essence division of labor further extraction agent of section.Smart subset uses rectifying column.Entering rectifying
Before tower, it is added into 80 DEG C or so of 5% temperature of hot water in rough segmentation material, and is sent into rectifying column together.Rectifying tower reboiler temperature
Degree is maintained at 105 DEG C or so, and overhead reflux temperature is maintained at 60 DEG C or so, and the top of the distillation column vacuum degree is maintained at -0.097MPa
Left and right.The mainly extractant produced at the top of rectifying column, tower bottom extraction essence divide material.Essence divide in material extract agent content be
0.1% or so；Divide material continuously to produce from the reboiler at rectifying column bottom essence, and is transported in purification evaporator and carries out
NMP purification and recovery.Purification evaporator is scraper-type evaporator, and external heat keeps in evaporator that temperature is at 105 DEG C or so, vacuum degree
It is maintained at -0.097MPa or so.NMP is produced at the top of evaporator, and rectifying waste liquid is discharged from base of evaporator,
The every 12h discharge of rectifying waste liquid is primary, is directly transported in settler.Anion is first added under agitation
Type polyacrylamide flocculant.Flocculant additive amount is the 2% of rectifying waste liquid, and flocculant aqueous solution concentration is 0.5%.10min
The aqueous sodium carbonate that 5% concentration is added afterwards carries out ion exchange and further precipitation process to rectifying waste liquid.It then will precipitating
Material filters pressing in device removes sediment.Filtrate is transported in the washing liquid storage tank after neutralizing, and then carries out extraction essence again
The processes such as evaporate.Sediment is as fixed-end forces；The NMP of purification is mixed with calcium chloride water, rectifying and dewatering is then carried out, obtains
It is lower than the NMP/ calcium chloride solution of 100ppm to moisture content.The cooled paradigmatic system that is transported to of the solution goes preparation p-phenylenediamine molten
Liquid starts to be recycled.
Embodiment 2:
Cleaning solution after being polymerize PPTA with calcium carbonate, which is neutralized to pH, reaches 6 or so.Then the cleaning solution after neutralization is defeated
It is sent in extraction tower and carries out extraction and separation, extractant is chloroform.Extraction tower bottom extraction extraction phase is sent to rough segmentation workshop section and is extracted
Take agent and the separation of NMP.The main equipment of rough segmentation is a falling film evaporator.Level-one evaporator keeps operation temperature on 80 DEG C of left sides
The right side, vacuum degree are maintained at -0.06MPa or so.Chloroform produces at the top of evaporator, and bottom produces rough segmentation material.In rough segmentation material
Agent content is extracted 15% or so；Rough segmentation material is sent to the essence division of labor further extraction agent of section.Smart subset uses rectifying
Tower.Before entering rectifying column, the hot water of 8% temperature 60 C or so is added into rough segmentation material, and be sent into rectifying column together.Essence
It evaporates tower reboiler temperature and is maintained at 105 DEG C or so, overhead reflux temperature is maintained at 50 DEG C or so, and the top of the distillation column vacuum degree is kept
In -0.095MPa or so.The mainly extractant produced at the top of rectifying column, tower bottom extraction essence divide material.Essence, which is divided in material, to be extracted
Agent content is 0.1% or so；Divide material continuously to produce from the reboiler at rectifying column bottom essence, and is transported to purification evaporator
Middle progress NMP purification and recovery.Purification evaporator be scraper-type evaporator, external heat keep evaporator in temperature at 105 DEG C or so,
Vacuum degree is maintained at -0.097MPa or so.NMP is produced at the top of evaporator, and rectifying waste liquid is discharged from base of evaporator, every 12h
Discharge is primary, is directly transported in settler.Anion-polyacrylamide flocculant is first added under agitation.Wadding
Solidifying agent additive amount is the 1% of rectifying waste liquid, and flocculant aqueous solution concentration is 0.2%.The potash water of 5% concentration is added after 5min
Solution carries out ion exchange and further precipitation process to rectifying waste liquid.Then by material filters pressing in settler, removing precipitating
Object.Filtrate is transported in the washing liquid storage tank after neutralizing, and then carries out the processes such as extracting rectifying again.Sediment is as solid waste
Processing；The NMP of purification is mixed with calcium chloride water, then carries out rectifying and dewatering, obtains moisture content lower than 100ppm's
NMP/ calcium chloride solution.The cooled paradigmatic system that is transported to of the solution goes to prepare p-phenylenediamine solution, starts to be recycled.
Embodiment 3:
Cleaning solution after being polymerize PPTA with calcium carbonate, which is neutralized to pH, reaches 6 or so.Then the cleaning solution after neutralization is defeated
It is sent in extraction tower and carries out extraction and separation, extractant is chloroform.Extraction tower bottom extraction extraction phase is sent to rough segmentation workshop section and is extracted
Take agent and the separation of NMP.The main equipment of rough segmentation is a plate tower.Destilling tower keeps operation temperature at 70 DEG C or so,
Vacuum degree is maintained at -0.06MPa or so.Chloroform produces at the top of evaporator, and bottom produces rough segmentation material.It is extracted in rough segmentation material
Agent content is 10% or so；Rough segmentation material is sent to the essence division of labor further extraction agent of section.Smart subset uses rectifying column.?
Into before rectifying column, it is added into 90 DEG C or so of 2% temperature of hot water in rough segmentation material, and is sent into rectifying column together.Rectifying column
Reboiler temperature is maintained at 110 DEG C or so, and overhead reflux temperature is maintained at 70 DEG C or so, and the top of the distillation column vacuum degree is maintained at-
0.096MPa or so.The mainly extractant produced at the top of rectifying column, tower bottom extraction essence divide material.Essence divides extractant in material to contain
Amount is 0.2% or so；By essence divide material continuously to produce from the reboiler at rectifying column bottom, and be transported to purification evaporator in into
Row NMP purification and recovery.Purification evaporator is scraper-type evaporator, and external heat keeps in evaporator that temperature is at 105 DEG C or so, vacuum
Degree is maintained at -0.097MPa or so.NMP is produced at the top of evaporator, and rectifying waste liquid is discharged from base of evaporator, every 12h discharge
Once, it is directly transported in settler.Anion-polyacrylamide flocculant is first added under agitation.Flocculant
Additive amount is the 1% of rectifying waste liquid, and flocculant aqueous solution concentration is 0.2%.The sodium hydroxide that 5% concentration is added after 5min is water-soluble
Liquid carries out ion exchange and further precipitation process to rectifying waste liquid.Then by material filters pressing in settler, sediment is removed.
Filtrate is transported in the washing liquid storage tank after neutralizing, and then carries out the processes such as extracting rectifying again.Sediment as solid waste at
Reason；The NMP of purification is mixed with calcium chloride water, then carries out rectifying and dewatering, obtains the NMP/ that moisture content is lower than 100ppm
Calcium chloride solution.The cooled paradigmatic system that is transported to of the solution goes to prepare p-phenylenediamine solution, starts to be recycled.
Embodiment 4:
Cleaning solution after being polymerize PPTA with calcium carbonate, which is neutralized to pH, reaches 6 or so.Then the cleaning solution after neutralization is defeated
It is sent in extraction tower and carries out extraction and separation, extractant is chloroform.Extraction tower bottom extraction extraction phase is sent to rough segmentation workshop section and is extracted
Take agent and the separation of NMP.The main equipment of rough segmentation is two falling film evaporators.Level-one evaporator keeps operation temperature on 60 DEG C of left sides
The right side, vacuum degree are maintained at -0.05MPa or so.Secondary evaporimeter keeps operation temperature at 85 DEG C or so, and vacuum degree is maintained at-
0.08MPa or so.Chloroform extraction at the top of two evaporators, bottom produce rough segmentation material.Agent content is extracted in rough segmentation material to exist
8% or so；Rough segmentation material is sent to the essence division of labor further extraction agent of section.Smart subset uses rectifying column.Entering rectifying
Before tower, it is added into the hot water of 2% temperature 50 C or so in rough segmentation material, and is sent into rectifying column together.Rectifying tower reboiler temperature
Degree is maintained at 100 DEG C or so, and overhead reflux temperature is maintained at 60 DEG C or so, and the top of the distillation column vacuum degree is maintained at -0.098MPa
Left and right.The mainly extractant produced at the top of rectifying column, tower bottom extraction essence divide material.Essence divide in material extract agent content be
0.1% or so；Divide material continuously to produce from the reboiler at rectifying column bottom essence, and is transported in purification evaporator and carries out
NMP purification and recovery.Purification evaporator is scraper-type evaporator, and external heat keeps in evaporator that temperature is at 105 DEG C or so, vacuum degree
It is maintained at -0.097MPa or so.NMP is produced at the top of evaporator, and rectifying waste liquid is discharged from base of evaporator, every 12h discharge one
It is secondary, directly it is transported in settler.Anion-polyacrylamide flocculant is first added under agitation.Flocculant adds
Dosage is the 2% of rectifying waste liquid, and flocculant aqueous solution concentration is 0.5%.The potassium hydroxide that 1% concentration is added after 10min is water-soluble
Liquid carries out ion exchange and further precipitation process to rectifying waste liquid.Then by material filtering in settler, sediment is removed.
Filtrate is transported in the washing liquid storage tank after neutralizing, and then carries out the processes such as extracting rectifying again.Sediment as solid waste at
Reason；The NMP of purification is mixed with calcium chloride water, then carries out rectifying and dewatering, obtains the NMP/ that moisture content is lower than 100ppm
Calcium chloride solution.The cooled paradigmatic system that is transported to of the solution goes to prepare p-phenylenediamine solution, starts to be recycled.
Claims (1)
1. a kind of para-aramid fiber production method for recovering solvents, which comprises the following steps:
(1) hydrochloric acid that in calcium carbonate and polymerization generates is added into the cleaning solution after PPTA polymerization, cleaning solution pH value is made to reach 5-7
Between；Cleaning solution after neutralization is transported in extraction tower and carries out extraction and separation, the extractant used is methylene chloride or trichlorine
Methane；Overhead extraction raffinate phase is extracted, tower bottom produces extraction phase；Extraction phase is transported to rough sorting device and carries out extractant and NMP
Separation, by raffinate phase conveying go carry out wastewater treatment；
(2) rough sorting device is using thin film evaporator or destilling tower and its ancillary equipment, under the conditions of decompression and heating evaporation, from extraction
It takes and removes extractant in phase；Rough sorting device keeps operation temperature between 50-90 DEG C, and vacuum degree is maintained at -0.05~-
Between 0.09MPa, extractant is produced at the top of rough sorting device, rough sorting device bottom produces rough segmentation material, extractant in rough segmentation material
Content is maintained between 10-20%；
(3) rough segmentation material addition hot water is sent to the further extraction agent of smart separating device together；Smart separating device uses rectifying column；
Hot water additive amount is the 2-10% of rough segmentation material, and hot water temperature is at 50-90 DEG C；The reboiler temperature of rectifying column is controlled in 100-
110 DEG C, overhead reflux temperature is controlled at 50-70 DEG C, and the top of the distillation column vacuum degree is maintained between -0.095~-0.098MPa；
Extraction includes extractant, water and NMP at the top of rectifying column, continuously produces essence in the reboiler at rectifying column bottom and divides material, essence divides material
Middle extraction agent content control is between 0.05-0.2%；
(4) material will be divided to be transported in purification evaporator from the essence continuously produced in the reboiler at rectifying column bottom and carries out NMP purifying
Recycling；Purification evaporator is scraper-type evaporator, heating outside evaporator, make in evaporator temperature be maintained at 100-110 DEG C it
Between, vacuum degree is maintained between -0.095~-0.098MPa；NMP is produced at the top of evaporator, it is useless that rectifying is discharged in base of evaporator
Liquid, the every 12h discharge of rectifying waste liquid are primary；
(5) rectifying waste liquid is transported in settler, is first added flocculant under agitation, be added after 5-10min salt or
Person's aqueous alkali carries out ion exchange and further precipitation process, the solution being disposed to rectifying waste liquid；Flocculant is
Anion or non-ionic polyacrylamide；Flocculant addition is the 1-5% of rectifying waste liquid, and flocculant is dissolved in by when use
The aqueous solution of concentration 0.1-1% is made into water；The additional amount of salt or alkali is subject to entire reaction system and no longer generates precipitating；Wherein
Salt includes sodium carbonate and potassium carbonate；Alkali includes sodium hydroxide and potassium hydroxide；Salt or alkali concentration control are in 1-5%；
(6) solution of step (5) being disposed is press-filtered out sediment with plate and frame filter press, the filtrate that filter press extrudes is again
Cleaning solution mixing after return step (1) and neutralization, and be transported to extraction tower and carry out extraction and separation, the precipitating that filter press extrudes
Object is as fixed-end forces；
(7) NMP that step (4) obtains is mixed with concentration 30-50% calcium chloride water, then carries out rectifying and dewatering, obtains
Moisture content is lower than the NMP/ calcium chloride solution of 100ppm, and dehydration afterchlorinate calcium concentration is stably held between 6-8%, by the solution
It is transported to paradigmatic system after cooling and prepares p-phenylenediamine solution, starts to carry out secondary cycle use.
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