CN114377421B - Lactic acid oligomerization and dewatering device - Google Patents
Lactic acid oligomerization and dewatering device Download PDFInfo
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- CN114377421B CN114377421B CN202210152071.8A CN202210152071A CN114377421B CN 114377421 B CN114377421 B CN 114377421B CN 202210152071 A CN202210152071 A CN 202210152071A CN 114377421 B CN114377421 B CN 114377421B
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- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 title claims abstract description 242
- 239000004310 lactic acid Substances 0.000 title claims abstract description 123
- 235000014655 lactic acid Nutrition 0.000 title claims abstract description 121
- 238000006384 oligomerization reaction Methods 0.000 title claims abstract description 76
- 239000011552 falling film Substances 0.000 claims abstract description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 238000010168 coupling process Methods 0.000 claims abstract description 30
- 238000005859 coupling reaction Methods 0.000 claims abstract description 30
- 230000008878 coupling Effects 0.000 claims abstract description 26
- 239000002994 raw material Substances 0.000 claims abstract description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 230000018044 dehydration Effects 0.000 claims abstract description 17
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 17
- 239000007788 liquid Substances 0.000 claims description 55
- 238000010992 reflux Methods 0.000 claims description 27
- 239000007791 liquid phase Substances 0.000 claims description 20
- 239000012071 phase Substances 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 10
- 239000002351 wastewater Substances 0.000 claims description 10
- 239000012295 chemical reaction liquid Substances 0.000 claims description 9
- 239000012074 organic phase Substances 0.000 claims description 7
- 239000003507 refrigerant Substances 0.000 claims description 6
- 238000007738 vacuum evaporation Methods 0.000 claims description 4
- 206010057040 Temperature intolerance Diseases 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 230000008543 heat sensitivity Effects 0.000 claims description 2
- 238000006116 polymerization reaction Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 16
- 229920000747 poly(lactic acid) Polymers 0.000 abstract description 11
- 239000004626 polylactic acid Substances 0.000 abstract description 11
- 238000005373 pervaporation Methods 0.000 abstract description 10
- 230000008569 process Effects 0.000 abstract description 8
- 230000002441 reversible effect Effects 0.000 abstract description 7
- 238000005265 energy consumption Methods 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 230000008901 benefit Effects 0.000 abstract description 2
- 238000004134 energy conservation Methods 0.000 abstract description 2
- 238000001704 evaporation Methods 0.000 abstract 1
- 230000008020 evaporation Effects 0.000 abstract 1
- 239000000047 product Substances 0.000 description 7
- 238000006068 polycondensation reaction Methods 0.000 description 5
- JJTUDXZGHPGLLC-UHFFFAOYSA-N lactide Chemical compound CC1OC(=O)C(C)OC1=O JJTUDXZGHPGLLC-UHFFFAOYSA-N 0.000 description 4
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 230000010354 integration Effects 0.000 description 3
- 229920000728 polyester Polymers 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000012718 coordination polymerization Methods 0.000 description 1
- 125000004122 cyclic group Chemical class 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000012690 ionic polymerization Methods 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 239000013502 plastic waste Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 238000007151 ring opening polymerisation reaction Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 238000005809 transesterification reaction Methods 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
- B01D5/0057—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes
- B01D5/006—Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes with evaporation or distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/0013—Controlling the temperature of the process
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
- C08G63/08—Lactones or lactides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/785—Preparation processes characterised by the apparatus used
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
The invention discloses a lactic acid oligomerization and dehydration device, and belongs to the technical field of polylactic acid production. By coupling the pervaporation and the rectification process, trace moisture in the lactic acid can be effectively removed, the problem of high energy consumption caused by independently adopting rectification is solved, meanwhile, the dehydration time is shortened, and the loss of raw material lactic acid is effectively reduced; the first-stage lactic acid oligomerization kettle, the falling film evaporation and the pervaporation are integrated, so that reaction generated water generated during the generation of lactic acid oligomer can be timely discharged, and further the reversible equilibrium reaction is effectively promoted; the two-stage lactic acid oligomerization falling film reactor is arranged, so that the effective control of the molecular weight of the lactic acid oligomer can be realized, and meanwhile, all water from the outside of rectification is collected into the rectification tower to recover a small amount of lactic acid contained in the water, so that the loss of raw material lactic acid is further reduced. The invention has the advantages of large load adjustment elasticity, simple operation, small equipment investment and energy conservation, and can finally effectively improve the utilization rate of lactic acid.
Description
Technical Field
The invention belongs to the technical field of polylactic acid production, and relates to a lactic acid oligomerization reaction and dehydration device.
Background
Biodegradable materials are polymeric materials that exhibit excellent properties during use, yet are readily enzymatically or microbiologically promoted to hydrolyze after use. Among various biodegradable materials, polylactic acid is receiving attention from the world because of its unique biocompatibility, degradability, and excellent processability. The polylactic acid product can be hydrolyzed in soil or water under the catalysis of enzymes or acid and alkali in microorganisms after being abandoned, and finally carbon dioxide and water are formed, so that the circulation in the nature is realized, and the environment is not polluted. The polylactic acid product has wide application prospect in agriculture, living field, clothing, medical industry and the like, such as agricultural mulching film, pesticide and fertilizer slow release material, disposable lunch box, various food and beverage outer packaging materials, various textiles with strong wrinkle resistance, good air permeability, comfortable wearing and the like. As can be seen, polylactic acid is an emerging degradable material, has considerable economic benefit and good application prospect, and is also an effective way for solving the problem of environmental pollution caused by plastic waste and relieving petroleum resource shortage.
The synthesis methods of polylactic acid mainly comprise two methods; one is direct polycondensation of lactic acid, the production process of the method is simple, but because impurities exist in the system and the polycondensation reaction of the lactic acid is reversible reaction, the obtained polylactic acid has smaller relative molecular weight and poor strength without practical value; another method for polylactic acid synthesis is a ring-opening polymerization reaction using cyclic dimer-lactide of lactic acid as a monomer. The method does not need to introduce special auxiliary agents, can obtain millions of products with high relative molecular mass through ionic polymerization or coordination polymerization, and becomes a main method for synthesizing polylactic acid. At present, lactic acid is synthesized into lactide by a decompression method, namely, lactic acid is taken as a raw material to be dehydrated under a vacuum condition to generate lactic acid oligomer, and then the oligomer is thermally cracked under the action of a catalyst, and further a reverse attack catalytic transesterification reaction, namely, a cyclization reaction is generated to generate lactide.
The reaction for generating the lactic acid oligomer in the first step is a polycondensation reaction for generating polyester between carboxyl and hydroxyl of the lactic acid, is a reversible equilibrium reaction, and has very small equilibrium constant, so that free water in the lactic acid and water generated by the reaction are discharged in time, and the reaction is necessary for generating the oligomer; the second step of lactide formation reaction, also called thermal chain extension reaction, is the reverse reaction of lactic acid polycondensation, and in fact, this is the main reason why direct polycondensation of lactic acid can only give low relative molecular mass products. In addition, lactide reacts with water to regenerate lactic acid. Therefore, in the oligomerization of lactic acid, it is necessary to discharge the free water and the reaction product water from the apparatus in time in the raw material pretreatment stage, the oligomerization stage, and the product purification stage
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a lactic acid oligomerization and dehydration device.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
A lactic acid oligomerization and dehydration device comprises an internal coupling rectifying tower, a No. 1 pervaporator, a primary lactic acid oligomerization kettle, a No.2 falling film evaporator, a secondary lactic acid oligomerization falling film reactor, a No.2 pervaporator and a lactic acid raw material pipeline;
The internal coupling rectifying tower is internally provided with a condensing section and an air lifting cap, a gas phase outlet at the top of the internal coupling rectifying tower is sequentially connected with a 1# primary condenser, a 1# gas-liquid separator, a 1# secondary condenser, a 2# gas-liquid separator and an inlet of a 1# vacuum pump, a liquid phase outlet of the 2# gas-liquid separator is sequentially connected with the 1# gas-liquid separator and an inlet of a wastewater pump, and an outlet of the wastewater pump is connected with a wastewater pipeline; the liquid phase outlet at the bottom of the lift cap is connected with the inlet of a No. 1 falling film evaporator, the outlet at the bottom of the No. 1 falling film evaporator is connected with the liquid phase inlet at the bottom of the internal coupling rectifying tower, the liquid phase outlet at the bottom of the internal coupling rectifying tower is connected with the inlet of a No. 1 reflux pump, and the pipeline at the outlet of the No. 1 reflux pump is divided into two branches which are respectively connected with the inlets of the No. 1 falling film evaporator and the No. 1 penetration evaporator; the water vapor outlet of the No. 1 pervaporator is connected with a water return port which is arranged at the upper part of the internal coupling rectifying tower and is close to the lower part of the condensing section, and the organic phase outlet of the internal coupling rectifying tower is connected with the inlet of a feed pipe of the primary lactic acid oligomerization kettle;
a stirrer, a feed pipe, a coil heat exchanger and an overflow weir are arranged in the primary lactic acid oligomerization kettle; the stirrer is connected with a driving motor to drive the stirrer to rotate and stir; the inlet of the feed pipe is connected with the organic phase outlet of the No. 1 pervaporator, and the outlet of the feed pipe is inserted into the bottom of the first-stage lactic acid oligomerization kettle and is close to the bottom surface; the coil heat exchanger is positioned below the liquid level of the primary lactic acid oligomerization kettle so as to control the temperature of the prepolymerization reaction; the overflow weir is arranged at the upper part of the first-stage lactic acid oligomerization kettle, and the reaction liquid overflows out of the polymerization kettle;
The inlet of the No. 2 falling film evaporator is connected with the outlet of an overflow weir of the first-stage lactic acid oligomerization kettle, the outlet of the bottom of the No. 2 falling film evaporator is connected with the inlet of the No. 3 gas-liquid separator, the liquid phase outlet of the No. 3 gas-liquid separator is connected with the inlet of the No. 2 reflux pump, and the outlet pipeline of the No. 2 reflux pump is divided into two branches which are respectively connected with the outlet pipeline of the No.1 reflux pump and the inlet of the second-stage lactic acid oligomerization falling film reactor;
The outlet of the bottom of the secondary lactic acid oligomerization falling film reactor is sequentially connected with the inlets of a No. 4 gas-liquid separator and a No. 3 reflux pump, and the outlet pipeline of the No. 3 reflux pump is divided into two branches which are respectively connected with the inlets of the secondary lactic acid oligomerization falling film reactor and a No. 2 pervaporator; the water vapor outlet of the No. 2 pervaporator is connected with the inlet of the No. 2 primary condenser, and the organic phase outlet of the No. 2 pervaporator is connected with a lactic acid oligomer pipeline; the outlet of the No. 2 primary condenser is sequentially connected with inlets of a No. 5 gas-liquid separator, a No. 2 secondary condenser, a No. 6 gas-liquid separator and a No. 2 vacuum pump, and the liquid phase outlet of the No. 6 gas-liquid separator is sequentially connected with inlets of a No. 5 gas-liquid separator and a water return pump;
the lactic acid raw material pipeline is connected with a raw material inlet in the middle of the internal coupling rectifying tower, an outlet of the backwater pump is connected with a water inlet between the raw material inlet and a backwater port from the No.1 pervaporator, and the No. 2 vacuum pump and a gas phase outlet pipeline of the No. 2 gas-liquid separator are combined into one inlet connected to the No.1 vacuum pump.
Further, the gas phase outlet pipes of the first stage lactic acid oligomerization kettle, the 3# gas-liquid separator, the 4# gas-liquid separator and the 2# pervaporator are combined into one inlet connected to the 2# first stage condenser.
Furthermore, the No.1 falling film evaporator, the No.2 falling film evaporator and the secondary lactic acid oligomerization falling film reactor all adopt falling film evaporators suitable for materials with high viscosity and high heat sensitivity to carry out vacuum evaporation dehydration.
Furthermore, the No. 1 secondary condenser and the No.2 secondary condenser adopt low-temperature refrigerant as refrigerant, so that substances easy to solidify can be prevented from entering the No. 1 vacuum pump and the No.2 vacuum pump, and the effect of protecting the vacuum pumps is achieved.
Further, the vacuum degree of the internal coupling rectifying tower is smaller than that of the primary lactic acid oligomerization kettle and the secondary lactic acid oligomerization falling film reactor.
Compared with the prior art, the invention has the following beneficial effects:
1. The invention has the characteristics of large load adjustment elasticity, simple operation, small equipment investment, small occupied area and energy saving, and can overcome the problems of high energy consumption and high investment when rectifying is singly adopted at the tail end of the lactic acid raw material for removing free water, namely, the trace water removal stage in lactic acid, by coupling the 1# pervaporation process with the rectification process, the pervaporation can effectively remove trace water in the lactic acid with extremely low energy consumption and investment, and simultaneously, the dehydration time is greatly shortened, and the lactic acid loss of the raw material is also extremely low;
2. The reaction water generated during the generation of the lactic acid oligomer can be timely discharged out of the oligomerization kettle through the further integration of the first-stage lactic acid oligomerization kettle, the No. 2 falling film evaporator and the No. 1 pervaporation, so that the reversible equilibrium reaction between carboxyl and hydroxyl of lactic acid is effectively promoted, and the reaction kettle moves towards the direction of generating polyester;
3. by arranging the secondary lactic acid oligomerization falling film reactor, the effective control of the molecular weight of the lactic acid oligomer can be realized, and meanwhile, the arranged 2# pervaporation is also a very effective and low-cost mode for removing trace moisture in the lactic acid oligomer product.
4. In addition, the water from the first-stage lactic acid oligomerization kettle, the 3# gas-liquid separator, the 4# gas-liquid separator, the 1# pervaporator and the 2# pervaporator are all converged into the rectifying tower, so that a small amount of lactic acid contained in the water can be effectively recovered, and the loss of raw material lactic acid is further reduced.
Drawings
FIG. 1 is a schematic diagram of a lactic acid oligomerization and dehydration apparatus according to the present invention.
In the figure, a 1-internal coupling rectifying tower; 2-a condensation section; 3-lifting an air cap; a 4-1# falling film evaporator; a 5-1# reflux pump; a 6-1# pervaporator; 7-a first-stage lactic acid oligomerization kettle; 8-coil heat exchanger; 9-overflow weir; 10-a stirrer; 11-3# gas-liquid separator; a 12-2# reflux pump; 13-2# falling film evaporator; a 14-secondary lactic acid oligomerization falling film reactor; 15-4# gas-liquid separator; 16-3# reflux pump; 17-a waste water pump; 18-1# primary condenser; 19-1# gas-liquid separator; a 20-1# two-stage condenser; 21-2# gas-liquid separator; 22-1# vacuum pump; 23-2# vacuum pump; 24-6# gas-liquid separator; a 25-2# two-stage condenser; 26-5# gas-liquid separator; a 27-2# primary condenser; 28-driving a motor; 29-a feed line; 30-a water return pump; 31-2# pervaporator; 40-lactic acid raw material pipeline; 41-an exhaust gas line; 42-a waste water pipeline; 43-lactic acid oligomer pipeline.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the attached drawing figures:
referring to fig. 1, a lactic acid oligomerization and dehydration device comprises an internal coupling rectifying tower 1, a # 1 falling film evaporator 4, a # 1 penetrating evaporator 6, a primary lactic acid oligomerization kettle 7, a # 2 falling film evaporator 13, a secondary lactic acid oligomerization falling film reactor 14, a # 2 penetrating evaporator 31, a # 1 vacuum pump 22 and a # 2 vacuum pump 23.
The lactic acid raw material containing free water enters an in-coupling rectifying tower 1 through a lactic acid raw material pipeline 40, flows downwards from top to bottom under the action of gravity, enters a 1# falling film evaporator 4 through an air lifting cap 3, the generated two-phase flow is separated from gas to liquid in the lower space of the air lifting cap 3 in the tower, the liquid phase flows through a 1# reflux pump 5 and is partially refluxed to the 1# falling film evaporator 4 again, part of the liquid phase flows as a produced flow, the gas phase flows from bottom to top through the air lifting cap 3, is subjected to stripping purification by reversely contacting with the lactic acid raw material and other feeding or reflux liquid in the in-coupling rectifying tower 1 to remove the moisture in the liquid phase, then the gas phase continuously moves upwards through a rectifying section, enters a condensing section 2, condenses all the lactic acid and part of the water vapor contained in the condensing section from top to bottom by gravity reflux, is again contacted with the gas phase in the in-coupling rectifying tower 1 to remove the moisture in the gas phase, the residual gas phase after the removal of the lactic acid is water vapor, and is subjected to the gas phase separation by a 1# primary condenser 18 and a 1# secondary condenser 20, and a gas phase 21 and a gas phase separator and a gas phase 21 are separated from the gas phase and a waste water pump 42 are discharged from the gas phase region through a waste water pump 41;
After the liquid from the outlets of the 1# reflux pump 5 and the 2# reflux pump 12 are converged, the liquid enters the 1# pervaporator 6, the water vapor outlet of the 1# pervaporator 6 is communicated with the water return port on the upper part of the internal coupling rectifying tower 1, which is close to the lower part of the condensing section 2, the converged liquid enters the internal coupling rectifying tower 1 to recover trace lactic acid therein, the organic phase outlet of the 1# pervaporator 6 is connected with the inlet of a feeding pipeline 29 of the first-stage lactic acid oligomerization kettle 7, the outlet of the feeding pipeline 29 is inserted into the bottom of the first-stage lactic acid oligomerization kettle 7, and the liquid is discharged near the bottom surface; the stirrer 10 is connected with a driving motor 28 to drive the stirrer 10 to stir in a rotating way; the coil heater 8 is positioned below the liquid level of the first-stage lactic acid oligomerization kettle 7 to control the oligomerization temperature; the overflow weir 9 is arranged at the upper part of the primary lactic acid oligomerization kettle 7, the reaction liquid overflows out of the primary lactic acid oligomerization kettle 7, and the height of the overflow weir 9 determines the liquid holdup of the primary lactic acid oligomerization kettle 7, namely the time of the primary oligomerization reaction.
Through the integration of the No. 1 pervaporator 6 and the internal coupling rectifying tower 1, the problems of high energy consumption and high investment in the process of independently rectifying the tail end of the lactic acid raw material for removing free water, namely, the trace water removal stage in lactic acid can be overcome, trace water in the lactic acid can be effectively removed by pervaporation with extremely low energy consumption and investment, meanwhile, the dehydration time is greatly shortened, and the loss of the lactic acid of the raw material is also extremely low.
The reaction liquid is sent into a No. 2 falling film evaporator 13 which is suitable for processing high-viscosity and high-heat-sensitivity materials through an overflow weir 9 outlet of a primary lactic acid oligomerization kettle 7, oligomerization reaction and vacuum evaporation are carried out on the reaction liquid, moisture in the reaction liquid is removed, gas-liquid separation is realized through a No. 3 gas-liquid separator 11, and after the liquid phase is partially converged with the extracted materials at the outlet of a No. 1 reflux pump 5 through a No. 2 reflux pump 12, and the partial liquid phase enters a secondary lactic acid oligomerization falling film reactor 14;
Through the integration of the processes of the first-stage lactic acid oligomerization kettle 7, the No. 2 falling film evaporator 13 and the No.1 pervaporation 6, the reaction generated water generated during the generation of lactic acid oligomer in the first-stage lactic acid oligomerization kettle 7 can be discharged out of the oligomerization kettle in time, so that the reversible equilibrium reaction between carboxyl and hydroxyl of lactic acid is effectively promoted, and the reaction moves towards the direction of polyester generation.
Finally, the reaction liquid is sent into a secondary lactic acid oligomerization falling film reactor 14 through a No. 2 reflux pump 12, oligomerization reaction and vacuum evaporation are carried out on the reaction liquid, moisture in the reaction liquid is removed, after gas-liquid separation is realized through a No. 4 gas-liquid separator 15, liquid phase is partially returned into an inlet of the secondary lactic acid oligomerization falling film reactor 14 through a No. 3 reflux pump 16, and partially enters a No. 2 pervaporation 31 to further remove trace moisture, and then the moisture is discharged out of the world through a lactic acid oligomer pipeline 43;
in the above process, the effective control of the molecular weight of the lactic acid oligomer can be realized by controlling the circulating amount of the material from the 3# reflux pump 16, and meanwhile, the arranged 2# pervaporation 31 is also a very effective and low-cost way for removing trace moisture in the lactic acid oligomer product.
In addition, after the water vapor from the first-stage lactic acid oligomerization kettle 7, the 3# gas-liquid separator 11, the 4# gas-liquid separator 15 and the 2# pervaporator 31 are converged, the two-stage condensation of the 2# first-stage condenser 27 and the 2# second-stage condenser 25 is carried out, and the two-stage gas-liquid separation of the 5# gas-liquid separator 26 and the 6# gas-liquid separator 24 is carried out, the liquid phase is sent into the internal coupling rectification tower 1 through the water return pump 30 so as to effectively recycle a small amount of lactic acid contained in the liquid phase, further reduce the loss of raw material lactic acid, and the gas phase is sent to the inlet of the 1# vacuum pump 22 through the 2# vacuum pump 23 because the vacuum degree of the internal coupling rectification tower 1 is smaller than that of the first-stage lactic acid oligomerization kettle 7 and the second-stage lactic acid oligomerization falling film reactor 14, so as to save the electric energy and investment of the vacuum pump.
Meanwhile, it should be noted that the second-stage condenser No. 120 and the second-stage condenser No. 2 25 use low-temperature refrigerant as a refrigerant, so as to prevent the easily solidified substances from entering the vacuum pump No. 122 and the vacuum pump No. 2 23, thereby protecting the vacuum pumps.
The analysis can prove that the lactic acid oligomerization reaction and dehydration device has the characteristics of ingenious design, small total occupied area, reduced engineering investment, high recovery rate, energy conservation, simple operation, high load adjustment elasticity, safety, reliability and the like, and can be applied to engineering; and provides a new optimized solving structure for the technical field of polylactic acid production.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (5)
1. The lactic acid oligomerization and dehydration device is characterized by comprising an internal coupling rectifying tower (1), a No. 1 pervaporator (6), a first-stage lactic acid oligomerization kettle (7), a No. 2 falling film evaporator (13), a second-stage lactic acid oligomerization falling film reactor (14), a No. 2 pervaporator (31) and a lactic acid raw material pipeline (40);
A condensing section (2) and an air lifting cap (3) are arranged in the internal coupling rectifying tower (1), a gas phase outlet at the top of the internal coupling rectifying tower (1) is sequentially connected with inlets of a 1# primary condenser (18), a 1# gas-liquid separator (19), a 1# secondary condenser (20), a 2# gas-liquid separator (21) and a 1# vacuum pump (22), a liquid phase outlet of the 2# gas-liquid separator (21) is sequentially connected with inlets of the 1# gas-liquid separator (19) and a wastewater pump (17), and an outlet of the wastewater pump (17) is connected with a wastewater pipeline (42); the liquid phase outlet at the bottom of the lift cap (3) is connected with the inlet of a No. 1 falling film evaporator (4), the outlet at the bottom of the No. 1 falling film evaporator (4) is connected with the liquid phase inlet at the bottom of the internal coupling rectifying tower (1), the liquid phase outlet at the bottom of the internal coupling rectifying tower (1) is connected with the inlet of a No. 1 reflux pump (5), and the pipeline at the outlet of the No. 1 reflux pump (5) is divided into two branches which are respectively connected with the inlets of the No. 1 falling film evaporator (4) and the No. 1 penetrating evaporator (6); the water vapor outlet of the No. 1 pervaporator (6) is connected with a water return port which is arranged at the upper part of the internal coupling rectifying tower (1) and is close to the lower part of the condensing section (2), and the organic phase outlet is connected with an inlet of a feed pipe (29) of the primary lactic acid oligomerization kettle (7);
A stirrer (10), a feed pipe (29), a coil heat exchanger (8) and an overflow weir (9) are arranged in the primary lactic acid oligomerization kettle (7); the stirrer (10) is connected with a driving motor (28) to drive the stirrer (10) to stir in a rotating way; the inlet of the feed pipe (29) is connected with the organic phase outlet of the No. 1 pervaporator (6), and the outlet of the feed pipe (29) is inserted into the bottom of the primary lactic acid oligomerization kettle (7) and is close to the bottom surface; the coil heat exchanger (8) is positioned below the liquid level of the primary lactic acid oligomerization kettle (7) so as to control the temperature of the prepolymerization reaction; the overflow weir (9) is arranged at the upper part of the first-stage lactic acid oligomerization kettle (7), and the reaction liquid overflows out of the polymerization kettle;
the inlet of the No. 2 falling film evaporator (13) is connected with the outlet of an overflow weir (9) of the first-stage lactic acid oligomerization kettle (7), the outlet of the bottom of the No. 2 falling film evaporator is connected with the inlet of a No. 3 gas-liquid separator (11), the liquid phase outlet of the No. 3 gas-liquid separator (11) is connected with the inlet of a No. 2 reflux pump (12), and the outlet pipeline of the No. 2 reflux pump (12) is divided into two branches which are respectively connected with the outlet pipeline of the No.1 reflux pump (5) and the inlet of the second-stage lactic acid oligomerization falling film reactor (14);
The outlet of the bottom of the secondary lactic acid oligomerization falling film reactor (14) is sequentially connected with inlets of a 4# gas-liquid separator (15) and a 3# reflux pump (16), and an outlet pipeline of the 3# reflux pump (16) is divided into two branches which are respectively connected with inlets of the secondary lactic acid oligomerization falling film reactor (14) and a 2# pervaporator (31); the water vapor outlet of the No. 2 pervaporator (31) is connected with the inlet of a No. 2 primary condenser (27), and the organic phase outlet is connected with a lactic acid oligomer pipeline (43); the outlet of the No. 2 primary condenser (27) is sequentially connected with inlets of a No. 5 gas-liquid separator (26), a No. 2 secondary condenser (25), a No. 6 gas-liquid separator (24) and a No. 2 vacuum pump (23), and the liquid phase outlet of the No. 6 gas-liquid separator (24) is sequentially connected with inlets of the No. 5 gas-liquid separator (26) and a water return pump (30);
The lactic acid raw material pipeline (40) is connected with a raw material inlet in the middle of the internal coupling rectifying tower (1), an outlet of the water return pump (30) is connected with a water inlet between the raw material inlet and a water return port from the 1# pervaporator (6) at the upper part of the internal coupling rectifying tower (1), and the gas phase outlet pipeline of the 2# vacuum pump (23) and the gas phase outlet pipeline of the 2# gas-liquid separator (21) are combined into one inlet connected to the 1# vacuum pump (22).
2. The lactic acid oligomerization and dehydration apparatus according to claim 1, wherein the gas phase outlet pipes of the primary lactic acid oligomerization tank (7), the 3# gas-liquid separator (11), the 4# gas-liquid separator (15) and the 2# pervaporator (31) are combined into one inlet connected to the 2# primary condenser (27).
3. The lactic acid oligomerization and dehydration apparatus according to claim 1, wherein the falling film evaporator # 1 (4), the falling film evaporator # 2 (13) and the secondary lactic acid oligomerization falling film reactor (14) are all falling film evaporators suitable for materials with high viscosity and high heat sensitivity, and are used for vacuum evaporation dehydration.
4. The lactic acid oligomerization and dehydration apparatus according to claim 1, wherein the 1# secondary condenser (20) and the 2# secondary condenser (25) use low-temperature refrigerant as a refrigerant to prevent easily coagulated substances from entering the 1# vacuum pump (22) and the 2# vacuum pump (23) to protect the vacuum pumps.
5. The lactic acid oligomerization and dehydration apparatus according to claim 1, wherein the vacuum degree of the in-coupling rectifying tower (1) is smaller than that of the primary lactic acid oligomerization kettle (7) and the secondary lactic acid oligomerization falling film reactor (14).
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| DE10020898B4 (en) * | 2000-04-20 | 2004-02-05 | Inventa-Fischer Gmbh | Process for the production of polylactic acid and device therefor |
| JP5291737B2 (en) * | 2010-02-26 | 2013-09-18 | 三洋化成工業株式会社 | Method for producing alkylene oxide adduct |
| CN102309865B (en) * | 2011-09-08 | 2014-06-04 | 中国石油天然气集团公司 | Refining system for circulating 1, 3-propanediol in continuous production of poly(trimethylene terephthalate) |
| EP2660270B1 (en) * | 2012-04-30 | 2023-10-25 | HDC POLYALL Co., Ltd. | Method for separating volatile substances from material mixtures and device for producing polyarylene sulphides |
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| CN106220501A (en) * | 2016-08-25 | 2016-12-14 | 江苏九天高科技股份有限公司 | A kind of water vapour penetration dehydration technique is for the method and apparatus of Synthesis of ethyl lactate |
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| CN109369607B (en) * | 2018-11-15 | 2023-08-01 | 凯瑞环保科技股份有限公司 | Device and method for synthesizing trioxymethylene through azeotropic catalytic reaction |
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| CN112934148A (en) * | 2019-11-26 | 2021-06-11 | 南京华基塔业有限公司 | Reaction system and method for oligomerization of lactic acid |
| CN111111572B (en) * | 2020-01-21 | 2023-10-20 | 中化学华陆新材料有限公司 | Supercritical CO in silicon-based aerogel production 2 Method for recovering dry solvent |
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