CN112876429A - Recovery method and recovery system of N-methylmorpholine-N-oxide - Google Patents
Recovery method and recovery system of N-methylmorpholine-N-oxide Download PDFInfo
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- CN112876429A CN112876429A CN202110072160.7A CN202110072160A CN112876429A CN 112876429 A CN112876429 A CN 112876429A CN 202110072160 A CN202110072160 A CN 202110072160A CN 112876429 A CN112876429 A CN 112876429A
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- LFTLOKWAGJYHHR-UHFFFAOYSA-N N-methylmorpholine N-oxide Chemical compound CN1(=O)CCOCC1 LFTLOKWAGJYHHR-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 56
- 238000011084 recovery Methods 0.000 title claims description 31
- 238000011282 treatment Methods 0.000 claims abstract description 183
- 238000000108 ultra-filtration Methods 0.000 claims abstract description 107
- 239000007788 liquid Substances 0.000 claims abstract description 102
- 239000000243 solution Substances 0.000 claims abstract description 86
- 229920000433 Lyocell Polymers 0.000 claims abstract description 53
- 230000015271 coagulation Effects 0.000 claims abstract description 42
- 238000005345 coagulation Methods 0.000 claims abstract description 42
- 238000005189 flocculation Methods 0.000 claims abstract description 33
- 230000016615 flocculation Effects 0.000 claims abstract description 33
- 238000004062 sedimentation Methods 0.000 claims abstract description 27
- 239000012535 impurity Substances 0.000 claims abstract description 23
- 150000003839 salts Chemical class 0.000 claims abstract description 22
- 239000011259 mixed solution Substances 0.000 claims abstract description 21
- 239000000701 coagulant Substances 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 239000000835 fiber Substances 0.000 claims abstract description 8
- 238000001728 nano-filtration Methods 0.000 claims description 230
- 239000000706 filtrate Substances 0.000 claims description 66
- 238000001223 reverse osmosis Methods 0.000 claims description 40
- 238000000502 dialysis Methods 0.000 claims description 39
- 238000001914 filtration Methods 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 239000012141 concentrate Substances 0.000 claims description 21
- 239000007787 solid Substances 0.000 claims description 16
- 238000001471 micro-filtration Methods 0.000 claims description 15
- 239000011347 resin Substances 0.000 claims description 13
- 229920005989 resin Polymers 0.000 claims description 13
- 238000007599 discharging Methods 0.000 claims description 6
- 230000001112 coagulating effect Effects 0.000 claims description 5
- 230000000717 retained effect Effects 0.000 claims description 3
- 230000000274 adsorptive effect Effects 0.000 claims 1
- 238000000746 purification Methods 0.000 claims 1
- 239000002351 wastewater Substances 0.000 abstract description 16
- 239000012528 membrane Substances 0.000 abstract description 10
- 238000005516 engineering process Methods 0.000 abstract description 6
- 239000000126 substance Substances 0.000 description 8
- 239000000084 colloidal system Substances 0.000 description 7
- 150000002500 ions Chemical class 0.000 description 7
- 239000002184 metal Chemical class 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000000049 pigment Chemical class 0.000 description 5
- 238000004064 recycling Methods 0.000 description 5
- 150000001720 carbohydrates Chemical class 0.000 description 4
- 238000004811 liquid chromatography Methods 0.000 description 4
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 150000001450 anions Chemical class 0.000 description 3
- 150000001768 cations Chemical class 0.000 description 3
- 238000007380 fibre production Methods 0.000 description 3
- 229920002521 macromolecule Polymers 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 150000004676 glycans Chemical class 0.000 description 2
- 229920002401 polyacrylamide Polymers 0.000 description 2
- 229920001282 polysaccharide Polymers 0.000 description 2
- 239000005017 polysaccharide Substances 0.000 description 2
- 239000002195 soluble material Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 239000000385 dialysis solution Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000003311 flocculating effect Effects 0.000 description 1
- 239000002608 ionic liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D295/00—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms
- C07D295/22—Heterocyclic compounds containing polymethylene-imine rings with at least five ring members, 3-azabicyclo [3.2.2] nonane, piperazine, morpholine or thiomorpholine rings, having only hydrogen atoms directly attached to the ring carbon atoms with hetero atoms directly attached to ring nitrogen atoms
- C07D295/24—Oxygen atoms
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a method and a system for recovering N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath, the method comprising: mixing the discharged liquid of the lyocell fiber coagulation bath with a coagulant aid to obtain a mixed liquid for flocculation and sedimentation; and carrying out ultrafiltration treatment on the mixed solution to obtain an ultrafiltration concentrated solution and an ultrafiltration clear solution. The method adopts the membrane technology to treat the lyocell fiber coagulation bath effluent, so that high COD impurities and high salt impurities can be removed step by step, the problem of wastewater difficult to treat in the lyocell fiber coagulation bath effluent treatment process in the prior art is solved, and the high-purity N-methylmorpholine-N-oxide can be efficiently recovered.
Description
Technical Field
The invention relates to the field of lyocell fiber production, in particular to a method and a system for recovering NMMO (N-methyl-MO) in coagulation bath discharge liquid of a lyocell fiber production process.
Background
In the process of producing the lyocell fiber, firstly dissolving the lyocell fiber pulp in high-content NMMO (N-methylmorpholine-N-oxide) ionic liquid, spraying the obtained mixture into pure water, separating out the lyocell fiber, and then producing a lyocell fiber product through subsequent refining, drying and other treatment processes; the liquid obtained after precipitation of lyocell fibers is called the effluent of the lyocell coagulation bath, and the NMMO content of the effluent is low due to dilution with pure water. The process for recovering NMMO from the effluent of a lyocell coagulation bath in the prior art mainly comprises the following steps: adding coagulant aid for flocculation and sedimentation, then using microporous filtration for clarification, using anion resin column and cation resin column to adsorb and purify impurities in the solution, and concentrating the purified NMMO solution to a certain content for reuse. When the anion and cation resin is saturated, sodium hydroxide and hydrochloric acid are needed to regenerate the ion resin, so that a large amount of alkaline and acidic wastewater with high COD equivalent is generated. And neutralizing the wastewater to obtain wastewater with high COD equivalent, high salt content and high chroma. This wastewater is the most important source of wastewater in lyocell fiber production and is difficult to treat due to the coexistence of high salt content and high COD equivalent in the wastewater.
Therefore, how to recover the NMMO in the effluent of the lyocell fiber coagulating bath in an environment-friendly way is a technical problem which needs to be solved in the field.
Disclosure of Invention
The invention mainly aims to provide a method and a system for recovering N-methylmorpholine-N-oxide, which are used for solving the problems that in the prior art, a large amount of wastewater with high COD equivalent and high salt content is generated in the process of recovering N-methylmorpholine-N-oxide in the effluent of a lyocell fiber coagulation bath, and secondary pollution is caused to the environment.
In order to achieve the above object, the present invention provides a method for recovering N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath, comprising:
mixing the discharged liquid of the lyocell fiber coagulation bath with a coagulant aid to obtain a mixed liquid for flocculation and sedimentation; and
and carrying out ultrafiltration treatment on the mixed solution to obtain an ultrafiltration concentrated solution and an ultrafiltration clear solution.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, which comprises the step of adsorbing and purifying the ultrafiltration filtrate by using ion resin.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, which also comprises the step of carrying out nanofiltration treatment on the ultrafiltration filtrate.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, wherein the nanofiltration treatment comprises primary nanofiltration treatment and secondary nanofiltration treatment; and the ultrafiltration clear liquid is subjected to the primary nanofiltration treatment to obtain a primary nanofiltration concentrated liquid and a primary nanofiltration clear liquid, the primary nanofiltration clear liquid is subjected to the secondary nanofiltration treatment to obtain a secondary nanofiltration concentrated liquid and a secondary nanofiltration clear liquid, and the N-methylmorpholine-N-oxide is retained in the secondary nanofiltration concentrated liquid.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, wherein the primary nanofiltration treatment also comprises the step of carrying out primary dialysis treatment on the primary nanofiltration concentrated solution by using water to obtain primary nanofiltration dialyzate, and the primary nanofiltration dialyzate and the primary nanofiltration clear filtrate are subjected to the secondary nanofiltration treatment; the number of the first-stage dialysis treatments is at least one.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, wherein the secondary nanofiltration treatment further comprises the step of carrying out secondary dialysis treatment on the secondary nanofiltration concentrated solution by using water to obtain secondary nanofiltration dialyzate; the number of the secondary dialysis treatments is at least one.
The method for recovering the N-methylmorpholine-N-oxide further comprises the step of carrying out reverse osmosis treatment on the secondary nanofiltration clear liquid and the secondary nanofiltration dialysate to obtain reverse osmosis concentrated liquid and reverse osmosis clear liquid containing monovalent salt impurities, wherein the reverse osmosis clear liquid is used as water for the primary dialysis treatment and the secondary dialysis treatment.
The recovery method of the N-methylmorpholine-N-oxide, provided by the invention, is characterized in that the filtration precision of the primary nanofiltration treatment is greater than or equal to 300-200 molecular weight, and the filtration precision of the secondary nanofiltration treatment is greater than or equal to 100-200 molecular weight.
The invention relates to a recovery method of N-methylmorpholine-N-oxide, wherein before the mixed solution is subjected to ultrafiltration treatment, the method also comprises the step of subjecting the mixed solution to microfiltration treatment to filter solid matters to obtain microporous filtrate; and carrying out ultrafiltration treatment on the microporous filtrate.
The invention relates to a recovery method of N-methylmorpholine-N-oxide, wherein the filtration precision of the microporous filtration treatment is 0.5-5 microns.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, wherein the ultrafiltration concentrated solution is recycled to the discharge liquid of the lyocell fiber coagulation bath for flocculation and sedimentation; the discharging liquid of the Lyocell fiber coagulating bath contains 150-250 g/L of N-methylmorpholine-N-oxide and has an electrical conductivity of 5-10000 us.
The invention relates to a method for recovering N-methylmorpholine-N-oxide, wherein the content of N-methylmorpholine-N-oxide in the primary nanofiltration concentrated solution and the primary nanofiltration clear filtrate is 140-250 g/L; the content of N-methylmorpholine-N-oxide in the primary nanofiltration concentrated solution after primary dialysis treatment is 0-10 g/L, and the content of N-methylmorpholine-N-oxide in the primary nanofiltration dialyzate is 1-100 g/L.
The recovery method of the N-methylmorpholine-N-oxide comprises the following steps of (1) enabling the content of the N-methylmorpholine-N-oxide in a secondary nanofiltration concentrated solution to be 140-250 g/L, enabling the conductivity to be 2-2000 us, enabling the content of the N-methylmorpholine-N-oxide in a secondary nanofiltration filtered liquid to be 0-5 g/L, and enabling the conductivity to be 2-2000 us; the content of N-methylmorpholine-N-oxide after the secondary nanofiltration concentrated solution is subjected to secondary dialysis treatment is 140-250 g/L, the conductivity is 1-5 us, the content of N-methylmorpholine-N-oxide in the secondary nanofiltration dialyzate is 0-5 g/L, and the conductivity is 1-1000 us.
In order to achieve the above object, the present invention also provides a recovery system of N-methylmorpholine-N-oxide from an effluent of a lyocell fibre coagulation bath, comprising:
the effluent of the lyocell fiber coagulation bath and the coagulant aid are introduced into the flocculation and sedimentation device to obtain a mixed solution for flocculation and sedimentation treatment; and
and the ultrafiltration treatment device is communicated with the flocculation sedimentation device so as to introduce the mixed solution into the ultrafiltration treatment device for ultrafiltration treatment to obtain ultrafiltration concentrated solution and ultrafiltration clear solution.
The recovery system of the N-methylmorpholine-N-oxide further comprises a primary nanofiltration treatment device and a secondary nanofiltration treatment device, wherein the primary nanofiltration treatment device is communicated with the ultrafiltration treatment device so as to convey the ultrafiltration filtrate to the primary nanofiltration treatment device for primary nanofiltration treatment to obtain primary nanofiltration concentrate and primary nanofiltration filtrate; and the secondary nanofiltration treatment device is communicated with the primary nanofiltration treatment device so as to convey the primary nanofiltration clear liquid to the secondary nanofiltration treatment device for secondary nanofiltration treatment to obtain secondary nanofiltration concentrated liquid and secondary nanofiltration clear liquid.
The recovery system of the N-methylmorpholine-N-oxide further comprises a reverse osmosis device which is communicated with the secondary nanofiltration treatment device so as to convey the secondary nanofiltration clear filtrate to the reverse osmosis device for reverse osmosis treatment.
The recovery system of N-methylmorpholine-N-oxide further comprises a microporous filtering device which is communicated with the flocculation settling device and the ultrafiltration treatment device, wherein the mixed solution is introduced into the microporous filtering device for microporous filtering treatment so as to filter solid matters to obtain microporous filtering solution, and the microporous filtering solution is introduced into the ultrafiltration treatment device for ultrafiltration treatment.
The invention has the beneficial effects that:
the method adopts the membrane technology to treat the lyocell fiber coagulation bath effluent, so that high COD impurities and high salt impurities can be removed step by step, the problem of wastewater difficult to treat in the lyocell fiber coagulation bath effluent treatment process in the prior art is avoided, and high-purity N-methylmorpholine-N-oxide can be efficiently recovered;
the method adopts the membrane technology to treat the discharged liquid of the lyocell fiber coagulating bath, and reduces or even does not use acid and alkali which pollute the environment; and the total amount of the wastewater is greatly reduced by recycling the reverse osmosis clear filtrate and using the subsequent evaporation condensate water for the dialysis water. Therefore, the treatment method has the advantages of low cost, low corrosion to equipment, high COD removal rate and less secondary pollution.
Drawings
FIG. 1 is a schematic view of a recovery system of N-methylmorpholine-N-oxide according to a first embodiment of the present invention;
FIG. 2 is a schematic view of a recovery system of N-methylmorpholine-N-oxide according to a second embodiment of the present invention;
FIG. 3 is a schematic view of a recovery system of N-methylmorpholine-N-oxide according to a third embodiment of the present invention;
FIG. 4 is a schematic view of a recovery system of N-methylmorpholine-N-oxide according to a fourth embodiment of the present invention;
FIG. 5 is a liquid chromatogram of the microporous filtrate of example 2 of the present invention;
FIG. 6 is a liquid chromatography chromatogram of the ultrafiltration concentrate of example 2 of the present invention;
FIG. 7 is a liquid chromatography chromatogram of the ultrafiltration filtrate of example 2 of the present invention;
FIG. 8 is a liquid chromatography spectrum of a primary nanofiltration filtrate in example 2 of the present invention;
FIG. 9 is a liquid chromatography chromatogram of a first-stage nanofiltration concentrate according to example 2 of the present invention.
Wherein, the reference numbers:
1 Lyocell fiber coagulation bath effluent
2 coagulant aid
3 ultrafiltering the concentrated solution
4 ultrafiltering the filtrate
5 solid matter
6 microporous filtering liquid
7 first-stage nanofiltration concentrated solution
8 first-stage nanofiltration clear filtrate
9 two-stage nanofiltration concentrate
10 two-stage nanofiltration filtrate
11 reverse osmosis concentrate
12 reverse osmosis clear filtrate
Flocculation and sedimentation device
B micropore filter equipment
C ultra-filtration treatment device
D first-stage nanofiltration treatment device
E secondary nanofiltration treatment device
F reverse osmosis device
Detailed Description
The following embodiments of the present invention will be described in detail, and the following embodiments are carried out on the premise of the technical scheme of the present invention to give detailed implementation procedures, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.
The present invention provides a process for the recovery of N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath, which process comprises, in a first embodiment:
mixing the discharged liquid of the lyocell fiber coagulation bath with a coagulant aid to obtain a mixed liquid for flocculation and sedimentation; and
and carrying out ultrafiltration treatment on the mixed solution to obtain an ultrafiltration concentrated solution and an ultrafiltration clear solution.
The discharge liquid of the lyocell fiber coagulation bath comprises NMMO, and also comprises impurities such as colloid, macromolecular organic matters, multivalent ions, pigments, metal complexes, saccharides, monovalent salts and the like. The method comprises the steps of firstly carrying out flocculation and sedimentation on the discharged liquid of the lyocell fiber coagulation bath to flocculate insoluble solid matters and colloids, then separating the solid matters through ultrafiltration treatment, and simultaneously trapping the colloids, macromolecular organic matters and the like in ultrafiltration concentrated liquid to obtain ultrafiltration filtrate subjected to primary impurity removal.
In this embodiment, the effluent of the lyocell fiber coagulation bath of the present invention has a content of N-methylmorpholine-N-oxide of 150 to 250 g/l, an electrical conductivity of 5 to 10000us, and is yellow; the coagulant aid is Polyacrylamide (PAM). The discharge liquid of the lyocell fiber coagulating bath is mixed with coagulant aid to obtain mixed liquid, and under the action of the coagulant aid, partial impurities in the mixed liquid are flocculated and settled. And then, carrying out ultrafiltration treatment on a mixed solution obtained by the discharge liquid of the lyocell fiber coagulation bath and a coagulant aid, wherein in the embodiment, the filtration precision of the ultrafiltration treatment is more than or equal to 1000-100000 molecular weight so as to retain insoluble solid matters, colloids, macromolecular organic matters and the like, and the target recovery matter NMMO enters ultrafiltration filtrate. Here, the filtration accuracy of the ultrafiltration treatment means that the ultrafiltration treatment can cut off substances having a molecular weight of 1000 to 100000 or more, for example, substances having a molecular weight of 1000, 2000, 3000, 10000 or more.
In the embodiment, flocculent, macromolecular impurities and the like in the discharge liquid of the lyocell fiber coagulation bath can be removed through the treatment to obtain the NMMO-containing solution with primary impurity removal, and then the NMMO-containing solution is concentrated to obtain the target recovered NMMO.
If the requirement on the purity of the NMMO is high, the ultrafiltration filtrate can be further adsorbed and purified by ion resin. Compared with the prior art in which the treatment method is directly carried out by using the ionic resin, the treatment method of the invention can greatly reduce the usage amount of the ionic resin and further reduce the generation of high COD and high salt wastewater because a great part of macromolecular substances, complex impurities and the like are removed by ultrafiltration treatment.
In another embodiment, before the ultrafiltration treatment of the mixed liquid obtained by the discharge liquid of the lyocell fiber coagulation bath and the coagulant aid, the method further comprises the steps of subjecting the mixed liquid to microfiltration treatment to filter solid matters to obtain microporous filtrate, wherein the microporous filtrate is yellow clear liquid; and performing ultrafiltration treatment on the obtained microporous filtrate. In another embodiment, the filtration precision of the microfiltration process is 0.5 to 5 μm. So, solid in the mixed liquid can be detached in the microfiltration, and the soluble material of macromolecule in the mixed liquid can be detached in ultrafiltration processing, goes on step by step, can improve edulcoration efficiency, reduces ultrafiltration processing's load capacity.
In addition, the content of NMMO in the ultrafiltration concentrated solution and the ultrafiltration clear solution is basically the same and is 150-250 g/L. In order to increase the NMMO recovery efficiency, in another embodiment, the ultrafiltration concentrate of the present invention is recycled to the effluent of the lyocell coagulation bath and subjected to flocculation settling again.
In a second embodiment, the method for recovering N-methylmorpholine-N-oxide of the present invention comprises:
mixing the discharged liquid of the lyocell fiber coagulation bath with a coagulant aid to obtain a mixed liquid for flocculation and sedimentation;
carrying out ultrafiltration treatment on the mixed solution to obtain an ultrafiltration concentrated solution and an ultrafiltration clear solution;
and (4) carrying out nanofiltration treatment on the ultrafiltration filtrate.
Here, the steps of performing flocculation and ultrafiltration treatment on the effluent of the lyocell coagulation bath are similar to those of the first embodiment, and are not described herein again, and only the differences will be described below.
In this embodiment, the nanofiltration treatment includes a primary nanofiltration treatment and a secondary nanofiltration treatment, but the present invention is not limited thereto. The ultrafiltration clear liquid is subjected to primary nanofiltration treatment to obtain primary nanofiltration concentrated liquid and primary nanofiltration clear liquid, the filtration precision of the primary nanofiltration treatment is larger than or equal to 300-1000 molecular weight, namely the primary nanofiltration treatment can intercept substances with the molecular weight larger than or equal to 300-1000, such as substances with the molecular weight larger than or equal to 300, 400, 500, 700, 900 and the like, so that the primary nanofiltration membrane intercepts saccharides such as multivalent ions, pigments, metal complexes, polysaccharides and the like in the primary nanofiltration concentrated liquid, and the target recovery NMMO and monovalent salt enter the primary nanofiltration clear liquid, so that the NMMO is further purified.
Wherein the contents of N-methylmorpholine-N-oxide in the primary nanofiltration concentrated solution and the primary nanofiltration clear solution are basically the same and are 150-250 g/L.
In order to improve the recovery efficiency of NMMO and reduce the waste of NMMO in the treatment process, the primary nanofiltration treatment also comprises primary dialysis treatment of the primary nanofiltration concentrated solution by using water to obtain primary nanofiltration dialysate, wherein the number of the primary dialysis treatment is at least one, and can be, for example, 2 times, 4 times, 6 times, 8 times and the like. The frequency of the first-stage dialysis treatment is mainly determined according to the content of NMMO in the dialyzed first-stage nanofiltration concentrated solution, and when the content of NMMO in the dialyzed first-stage nanofiltration concentrated solution is reduced to an acceptable range, for example, the content of N-methylmorpholine-N-oxide in the first-stage nanofiltration concentrated solution after the first-stage dialysis treatment is 0-10 g/L, the first-stage dialysis treatment can be stopped, and the first-stage nanofiltration concentrated solution is discharged. At this time, all the obtained first-stage nanofiltration dialyzates are mixed, wherein the content of the N-methylmorpholine-N-oxide is generally 10-100 g/L.
And performing secondary nanofiltration treatment on all the obtained primary nanofiltration dialysate and the primary nanofiltration clear liquid together to obtain secondary nanofiltration concentrated liquid and secondary nanofiltration clear liquid, wherein the N-methylmorpholine-N-oxide is trapped in the secondary nanofiltration concentrated liquid.
In this embodiment, the filtration precision of the secondary nanofiltration treatment is greater than or equal to 100-200 molecular weight, that is, the secondary nanofiltration treatment can intercept substances with molecular weight greater than or equal to 100-200, such as substances with molecular weight greater than or equal to 100, 150, 200, etc., so that the target recovered NMMO is intercepted in the secondary nanofiltration concentrate, and monovalent salt and solvent water enter the secondary nanofiltration filtrate, so that NMMO is further purified and primarily concentrated.
The content of N-methylmorpholine-N-oxide in the secondary nanofiltration concentrated solution is 150-250 g/L, the conductivity is 2-500 us, the content of N-methylmorpholine-N-oxide in the secondary nanofiltration clear filtrate is 0-5 g/L, and the conductivity is 2-300 us. At the moment, part of monovalent salt still exists in the secondary nanofiltration concentrated solution, in order to further purify NMMO and remove impurities in the NMMO, the secondary nanofiltration treatment also comprises the step of carrying out secondary dialysis treatment on the secondary nanofiltration concentrated solution by using water to obtain secondary nanofiltration dialyzate; the number of the secondary dialysis treatments is at least one, and may be, for example, 2, 4, 6, 8, or the like. The number of times of the secondary dialysis treatment is mainly determined according to the content of monovalent salt in the secondary nanofiltration concentrated solution, for example, the content of N-methylmorpholine-N-oxide after the secondary dialysis treatment of the secondary nanofiltration concentrated solution is 150-250 g/L, the conductivity is 1-5 us, the content of N-methylmorpholine-N-oxide in the secondary nanofiltration dialyzate is 0-5 g/L, and the secondary dialysis treatment can be stopped when the conductivity is 1-1000 us.
The secondary nanofiltration clear filtrate and the secondary nanofiltration dialysate can be subjected to reverse osmosis treatment to obtain reverse osmosis concentrated solution and reverse osmosis clear filtrate containing monovalent salt impurities, and the reverse osmosis clear filtrate is used as water for the primary dialysis treatment and the secondary dialysis treatment so as to save water resources and reduce wastewater; and (4) discharging the reverse osmosis concentrated solution or further treating.
In another embodiment, the invention judges the concentration multiple of the reverse osmosis treatment according to the conductivity of the reverse osmosis filtered liquid, for example, the conductivity of the reverse osmosis filtered liquid is less than 1 us.
The impurity removal rate of the secondary nanofiltration concentrated solution obtained by the invention is more than 95 percent, the purity of NMMO in the coagulation bath discharge liquid is greatly improved, the difficulty of the subsequent recovery process is reduced, and the generation of 90 percent of high-salinity wastewater is reduced. The treatment technology can realize the recovery and utilization of NMMO in the coagulation bath discharge liquid, reduce the discharge of related waste water and reduce the dosage of acid and alkali; in addition, the method has the characteristics of convenient operation, energy conservation, small corrosion to equipment, low cost and no exogenous pollution, and greatly improves the economic benefit by recycling resources.
The invention thus proposes to treat the effluent of a lyocell fibre coagulation bath using membrane technology to recover the NMMO therein. Specifically, the molecular weight cutting is carried out on the discharged liquid by utilizing the difference of the molecular weight cut-off and the surface electrical property of the membrane, and the impurities and the NMMO are separated step by step so as to achieve the purpose of purifying and recovering the NMMO. The treatment technology of the invention greatly reduces the usage amount of the ionic resin, even does not use the ionic resin, stops or greatly reduces the generation of high-salt and high-COD coexisting wastewater, and can obtain high-purity NMMO with high efficiency.
The present invention also provides a recovery system of N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath, as shown in figure 1, the recovery system of the first embodiment of the present invention comprising a flocculating and settling apparatus a and an ultrafiltration treatment apparatus C.
Wherein, the discharge liquid 1 of the lyocell fiber coagulation bath and the coagulant aid 2 are introduced into the flocculation sedimentation device A and mixed to obtain a mixed liquid for flocculation sedimentation treatment;
and the ultrafiltration treatment device C is communicated with the flocculation sedimentation device A, so that the mixed solution is introduced into the ultrafiltration treatment device C for ultrafiltration treatment to obtain an ultrafiltration concentrated solution 3 and an ultrafiltration clear solution 4.
In this embodiment, the filtration precision of the ultrafiltration treatment apparatus C of the present invention is greater than or equal to 1000 to 100000 molecular weight, that is, the filtration precision of the ultrafiltration membrane in the ultrafiltration treatment apparatus C of the present invention is greater than or equal to 1000 to 100000 molecular weight, so as to retain insoluble solid, colloid, macromolecular organic matter, etc., and the target recovered substance NMMO enters the ultrafiltration filtrate 4.
Referring to fig. 2, the recycling system of N-methylmorpholine-N-oxide according to the second embodiment of the present invention further includes a microporous filtering apparatus B, and other apparatuses are the same as those in the first embodiment and are not described herein again. And the microporous filtering device B is communicated with the flocculation settling device A and the ultrafiltration treatment device C, the mixed solution is introduced into the microporous filtering device B for microporous filtering treatment to filter solid 5 to obtain microporous filtering solution 6, and the microporous filtering solution 6 is introduced into the ultrafiltration treatment device C for ultrafiltration treatment.
In order to improve the NMMO recovery efficiency, the ultrafiltration concentrate 3 of the present invention can be recycled to the flocculation and sedimentation device A, mixed with the effluent 1 of the lyocell coagulation bath, and subjected to flocculation and sedimentation again.
In this embodiment, the filtration precision of the microporous filter device B is 0.5 to 5 μm. So, solid in the mixed liquid can be detached in the microfiltration, and the soluble material of macromolecule in the mixed liquid can be detached in ultrafiltration processing, goes on step by step, can improve edulcoration efficiency, reduces ultrafiltration processing's load capacity.
Referring to fig. 3, a recycling system of N-methylmorpholine-N-oxide according to a third embodiment of the present invention includes: a flocculation sedimentation device A, an ultrafiltration treatment device C, a primary nanofiltration treatment device D and a secondary nanofiltration treatment device E.
The primary nanofiltration treatment device D is communicated with the ultrafiltration treatment device C, so that the ultrafiltration filtrate 4 is conveyed to the primary nanofiltration treatment device D for primary nanofiltration treatment to obtain primary nanofiltration concentrate 7 and primary nanofiltration filtrate 8; and the secondary nanofiltration treatment device E is communicated with the primary nanofiltration treatment device D so as to convey the primary nanofiltration clear filtrate 8 to the secondary nanofiltration treatment device E for secondary nanofiltration treatment to obtain secondary nanofiltration concentrated solution 9 and secondary nanofiltration clear filtrate 10.
The flocculation and sedimentation device a and the ultrafiltration treatment device C of this embodiment are similar to those of the first embodiment, and are not described in detail here.
In this embodiment, the filtration precision of the first-stage nanofiltration treatment device D is greater than or equal to 300-1000 molecular weight, so that the first-stage nanofiltration membrane can retain multivalent ions, pigments, metal complexes and saccharides in the first-stage nanofiltration concentrated solution 7, and the target recovery NMMO and monovalent salt enter the first-stage nanofiltration clear solution 8, so that the NMMO can be further purified.
In this embodiment, the filtration accuracy of the secondary nanofiltration treatment device E is greater than or equal to 100-200 molecular weight, so that the target recovered NMMO is retained in the secondary nanofiltration concentrate 9, and monovalent salt and solvent water enter the secondary nanofiltration filtrate 10, so that NMMO is further purified and primarily concentrated.
Referring to fig. 4, the recycling system of N-methylmorpholine-N-oxide according to the fourth embodiment of the present invention further includes a reverse osmosis apparatus F, which is similar to the third embodiment and will not be described herein again. And the reverse osmosis device F is communicated with the secondary nanofiltration treatment device E so as to convey the secondary nanofiltration clear filtrate 10 to the reverse osmosis device F for reverse osmosis treatment to obtain reverse osmosis concentrated solution 11 containing monovalent salt impurities and reverse osmosis clear filtrate 12.
The reverse osmosis clear filtrate 12 can be recycled to the primary nanofiltration treatment device D and the secondary nanofiltration treatment device E to be used as water for primary dialysis treatment and secondary dialysis treatment so as to save water resources and reduce the generation of wastewater; and discharging the reverse osmosis concentrated solution 11 or further treating.
The technical scheme of the invention is further explained in detail by specific embodiments, in the following embodiments, the discharge liquid of the lyocell fiber coagulation bath comes from the production process of lyocell fibers, wherein the NMMO content is about 150-250 g/L; the conductivity is about 5-10000 us, and the liquid is yellow liquid.
Example 1
and 2, carrying out ultrafiltration treatment on the mixed solution obtained in the step 1, wherein the cut-off molecular weight is 80000-.
Conveying the ultrafiltration filtrate to an anion resin column to remove organic impurities such as pigments, saccharides and the like and metal complexes; and then metal ions are removed through a cation resin column, and pure NMMO is obtained through concentration.
Example 2
And 3, performing ultrafiltration treatment on the microporous filter liquid, wherein the intercepted molecular weight is 10000-30000 daltons, so as to intercept small-particle-size solids, colloids and macromolecular impurities, the obtained ultrafiltration concentrated liquid is 5% of the volume of the microporous filter liquid, the NMMO content in the ultrafiltration concentrated liquid and the ultrafiltration clear liquid is both 150-250 g/l, and the ultrafiltration concentrated liquid returns to the step 1 for repeated flocculation. The liquid chromatogram of the obtained ultrafiltration concentrate is shown in fig. 6, the liquid chromatogram of the ultrafiltration clear liquid is shown in fig. 7, wherein peak 1 is the characteristic peak of NMMO, and comparing fig. 7 with fig. 5 shows that the purity of NMMO in the ultrafiltration clear liquid is improved.
The liquid chromatogram of the obtained primary nanofiltration clear liquid is shown in fig. 8, and the liquid chromatogram of the dialyzed primary nanofiltration concentrated liquid is shown in fig. 9, wherein the peak 1 is the characteristic peak of NMMO. As shown in FIG. 9, the residual NMMO in the first-stage nanofiltration concentrate is small, so that NMMO is not wasted, and the NMMO recovery efficiency can be improved. Comparing fig. 8 and fig. 7, the purity of NMMO in the first nanofiltration filtrate is improved.
And 6, mixing the secondary nanofiltration filtrate with the secondary nanofiltration dialysate, and performing reverse osmosis treatment to ensure that the conductivity of the reverse osmosis filtrate is less than 1us, wherein the reverse osmosis filtrate can be used as dialysis water for primary dialysis treatment and secondary dialysis treatment.
Table 1 below shows the NMMO content data in the above stages.
TABLE 1 NMMO content in the stages
Example 3
and 2, carrying out ultrafiltration treatment on the mixed solution obtained in the step 1, wherein the molecular weight cutoff is 5000-10000 Dalton, solid matter, colloid and macromolecular impurities are cut off, the volume of the obtained ultrafiltration concentrated solution is 8% of that of the mixed solution, the NMMO content in the ultrafiltration concentrated solution and the ultrafiltration clear solution is 150-10000 g/L, and the ultrafiltration concentrated solution returns to the step 1 for repeated flocculation.
And 6, mixing the secondary nanofiltration filtrate with the secondary nanofiltration dialysate, and performing reverse osmosis treatment to ensure that the conductivity of the reverse osmosis filtrate is less than 1us, wherein the reverse osmosis filtrate can be used as dialysis water for primary dialysis treatment and secondary dialysis treatment.
The present invention is capable of other embodiments, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (17)
1. A process for the recovery of N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath, the process comprising:
mixing the discharged liquid of the lyocell fiber coagulation bath with a coagulant aid to obtain a mixed liquid for flocculation and sedimentation; and
and carrying out ultrafiltration treatment on the mixed solution to obtain an ultrafiltration concentrated solution and an ultrafiltration clear solution.
2. The method of claim 1, further comprising subjecting the ultrafiltration filtrate to adsorptive purification using an ionic resin.
3. The method of claim 1, further comprising subjecting the ultrafiltration filtrate to nanofiltration.
4. The method of claim 3, wherein the nanofiltration treatment comprises a primary nanofiltration treatment and a secondary nanofiltration treatment; and the ultrafiltration clear liquid is subjected to the primary nanofiltration treatment to obtain a primary nanofiltration concentrated liquid and a primary nanofiltration clear liquid, the primary nanofiltration clear liquid is subjected to the secondary nanofiltration treatment to obtain a secondary nanofiltration concentrated liquid and a secondary nanofiltration clear liquid, and the N-methylmorpholine-N-oxide is retained in the secondary nanofiltration concentrated liquid.
5. The method of claim 4, wherein the primary nanofiltration treatment further comprises subjecting the primary nanofiltration concentrate to a primary dialysis treatment using water to obtain a primary nanofiltration dialysate, and subjecting the primary nanofiltration dialysate and the primary nanofiltration filtrate to the secondary nanofiltration treatment; the number of the first-stage dialysis treatments is at least one.
6. The method of claim 5, wherein the secondary nanofiltration treatment further comprises subjecting the secondary nanofiltration concentrate to a secondary dialysis treatment with water to obtain a secondary nanofiltration dialysate; the number of the secondary dialysis treatments is at least one.
7. The method of claim 6, further comprising subjecting the secondary nanofiltration filtrate and the secondary nanofiltration dialysate to reverse osmosis to obtain a reverse osmosis concentrate and a reverse osmosis filtrate containing monovalent salt impurities, wherein the reverse osmosis filtrate is used as the water for the primary dialysis treatment and the secondary dialysis treatment.
8. The method as claimed in claim 4, wherein the primary nanofiltration treatment has a filtration precision of greater than or equal to 300-1000 molecular weight, and the secondary nanofiltration treatment has a filtration precision of greater than or equal to 100-200 molecular weight.
9. The method for recovering N-methylmorpholine-N-oxide as claimed in claim 1 or 7, wherein the step of subjecting the mixed liquor to ultrafiltration further comprises subjecting the mixed liquor to microfiltration treatment to filter solids and obtain a microfiltration solution; and carrying out ultrafiltration treatment on the microporous filtrate.
10. The method for recovering N-methylmorpholine-N-oxide as claimed in claim 9, wherein the filtration precision of the microfiltration treatment is 0.5 to 5 μm.
11. The method of claim 9, wherein the ultrafiltration concentrate is recycled to the effluent of the lyocell coagulation bath for flocculation and sedimentation; the discharging liquid of the Lyocell fiber coagulating bath contains 150-250 g/L of N-methylmorpholine-N-oxide and has an electrical conductivity of 5-10000 us.
12. The method for recovering N-methylmorpholine-N-oxide as claimed in claim 5, wherein the content of N-methylmorpholine-N-oxide in the primary nanofiltration concentrate and the primary nanofiltration filtrate is 140-250 g/L; the content of N-methylmorpholine-N-oxide in the primary nanofiltration concentrated solution after primary dialysis treatment is 0-10 g/L, and the content of N-methylmorpholine-N-oxide in the primary nanofiltration dialyzate is 1-150 g/L.
13. The method for recovering N-methylmorpholine-N-oxide as claimed in claim 6, wherein the content of N-methylmorpholine-N-oxide in the secondary nanofiltration concentrate is 140-250 g/l, the conductivity is 2-2000 us, the content of N-methylmorpholine-N-oxide in the secondary nanofiltration filtrate is 0-5 g/l, and the conductivity is 2-2000 us; the content of N-methylmorpholine-N-oxide after the secondary nanofiltration concentrated solution is subjected to secondary dialysis treatment is 140-250 g/L, the conductivity is 1-5 us, the content of N-methylmorpholine-N-oxide in the secondary nanofiltration dialyzate is 0-5 g/L, and the conductivity is 1-1000 us.
14. A recovery system for N-methylmorpholine-N-oxide from the effluent of a lyocell fibre coagulation bath comprising:
the effluent of the lyocell fiber coagulation bath and the coagulant aid are introduced into the flocculation and sedimentation device to obtain a mixed solution for flocculation and sedimentation treatment; and
and the ultrafiltration treatment device is communicated with the flocculation sedimentation device so as to introduce the mixed solution into the ultrafiltration treatment device for ultrafiltration treatment to obtain ultrafiltration concentrated solution and ultrafiltration clear solution.
15. The system of claim 14, further comprising a primary nanofiltration treatment device and a secondary nanofiltration treatment device, wherein the primary nanofiltration treatment device is in communication with the ultrafiltration treatment device to deliver the ultrafiltration filtrate to the primary nanofiltration treatment device for primary nanofiltration treatment to obtain a primary nanofiltration concentrate and a primary nanofiltration filtrate; and the secondary nanofiltration treatment device is communicated with the primary nanofiltration treatment device so as to convey the primary nanofiltration clear liquid to the secondary nanofiltration treatment device for secondary nanofiltration treatment to obtain secondary nanofiltration concentrated liquid and secondary nanofiltration clear liquid.
16. The system for recovery of N-methylmorpholine-N-oxide as claimed in claim 15 further comprising a reverse osmosis unit in communication with the secondary nanofiltration treatment unit for conveying the secondary nanofiltration filtrate to the reverse osmosis unit for reverse osmosis treatment.
17. A system for recovering N-methylmorpholine-N-oxide as claimed in claim 14 or claim 15 further comprising a microfiltration device in communication with the flocculation and sedimentation device and the ultrafiltration treatment device, wherein the mixed liquor is passed through the microfiltration device for microfiltration treatment to filter solids and obtain a microfiltration solution, and the microfiltration solution is passed through the ultrafiltration treatment device for ultrafiltration treatment.
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