CN111097358B - Continuous synthesis reaction recovery system and method for polyamide - Google Patents
Continuous synthesis reaction recovery system and method for polyamide Download PDFInfo
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- CN111097358B CN111097358B CN201911233353.5A CN201911233353A CN111097358B CN 111097358 B CN111097358 B CN 111097358B CN 201911233353 A CN201911233353 A CN 201911233353A CN 111097358 B CN111097358 B CN 111097358B
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- 238000011084 recovery Methods 0.000 title claims abstract description 52
- 239000004952 Polyamide Substances 0.000 title claims abstract description 43
- 229920002647 polyamide Polymers 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000003786 synthesis reaction Methods 0.000 title claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 176
- 150000004985 diamines Chemical class 0.000 claims abstract description 66
- 239000007791 liquid phase Substances 0.000 claims abstract description 66
- 239000012071 phase Substances 0.000 claims abstract description 24
- 238000006068 polycondensation reaction Methods 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 150000003839 salts Chemical class 0.000 claims abstract description 10
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 6
- 230000006837 decompression Effects 0.000 claims description 28
- 239000000243 solution Substances 0.000 claims description 7
- 238000003860 storage Methods 0.000 claims description 7
- 238000010924 continuous production Methods 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 4
- RKLJSFSLDCKWPH-UHFFFAOYSA-N C(CCCCC(=O)O)(=O)O.C(CCCC)(N)N Chemical compound C(CCCCC(=O)O)(=O)O.C(CCCC)(N)N RKLJSFSLDCKWPH-UHFFFAOYSA-N 0.000 claims description 2
- PMOAZSKERZBZBB-UHFFFAOYSA-N C(CCCCC)(N)N.C(CCCCCCCCC(=O)O)(=O)O Chemical compound C(CCCCC)(N)N.C(CCCCCCCCC(=O)O)(=O)O PMOAZSKERZBZBB-UHFFFAOYSA-N 0.000 claims description 2
- JHWNWJKBPDFINM-UHFFFAOYSA-N Laurolactam Chemical class O=C1CCCCCCCCCCCN1 JHWNWJKBPDFINM-UHFFFAOYSA-N 0.000 claims description 2
- 239000012267 brine Substances 0.000 claims description 2
- MUPZPRBKMCLFOX-UHFFFAOYSA-N butane-1,1-diamine;hexanedioic acid Chemical compound CCCC(N)N.OC(=O)CCCCC(O)=O MUPZPRBKMCLFOX-UHFFFAOYSA-N 0.000 claims description 2
- QRRJJSBORXYXCS-UHFFFAOYSA-N hexane-1,1-diamine terephthalic acid Chemical compound CCCCCC(N)N.OC(=O)c1ccc(cc1)C(O)=O QRRJJSBORXYXCS-UHFFFAOYSA-N 0.000 claims description 2
- -1 hexanediamine dodecacarbonate Chemical compound 0.000 claims description 2
- 229940116351 sebacate Drugs 0.000 claims description 2
- CXMXRPHRNRROMY-UHFFFAOYSA-L sebacate(2-) Chemical compound [O-]C(=O)CCCCCCCCC([O-])=O CXMXRPHRNRROMY-UHFFFAOYSA-L 0.000 claims description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims description 2
- QFNNDGVVMCZKEY-UHFFFAOYSA-N azacyclododecan-2-one Chemical class O=C1CCCCCCCCCCN1 QFNNDGVVMCZKEY-UHFFFAOYSA-N 0.000 claims 1
- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical class O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 claims 1
- 238000006116 polymerization reaction Methods 0.000 abstract description 15
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- WYTGDNHDOZPMIW-RCBQFDQVSA-N alstonine Natural products C1=CC2=C3C=CC=CC3=NC2=C2N1C[C@H]1[C@H](C)OC=C(C(=O)OC)[C@H]1C2 WYTGDNHDOZPMIW-RCBQFDQVSA-N 0.000 description 13
- 229920002302 Nylon 6,6 Polymers 0.000 description 9
- 230000009471 action Effects 0.000 description 9
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 8
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- 238000000926 separation method Methods 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 239000000289 melt material Substances 0.000 description 4
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- 239000004677 Nylon Substances 0.000 description 2
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- 238000003541 multi-stage reaction Methods 0.000 description 2
- 229920001778 nylon Polymers 0.000 description 2
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- 230000002269 spontaneous effect Effects 0.000 description 2
- 125000003277 amino group Chemical group 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
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- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
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- 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
- B01J19/24—Stationary reactors without moving elements inside
- B01J19/2455—Stationary reactors without moving elements inside provoking a loop type movement of the reactants
- B01J19/246—Stationary reactors without moving elements inside provoking a loop type movement of the reactants internally, i.e. the mixture circulating inside the vessel such that the upward stream is separated physically from the downward stream(s)
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/82—Purification; Separation; Stabilisation; Use of additives
- C07C209/86—Separation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C211/00—Compounds containing amino groups bound to a carbon skeleton
- C07C211/01—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to acyclic carbon atoms
- C07C211/02—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to acyclic carbon atoms of an acyclic saturated carbon skeleton
- C07C211/09—Diamines
- C07C211/12—1,6-Diaminohexanes
-
- 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
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
- C08G69/265—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids from at least two different diamines or at least two different dicarboxylic acids
-
- 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
- C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
- C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
- C08G69/26—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from polyamines and polycarboxylic acids
- C08G69/28—Preparatory processes
-
- 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
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00002—Chemical plants
- B01J2219/00027—Process aspects
- B01J2219/00033—Continuous processes
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- 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
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00051—Controlling the temperature
- B01J2219/00054—Controlling or regulating the heat exchange system
-
- 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
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00051—Controlling the temperature
- B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
- B01J2219/00076—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements inside the reactor
- B01J2219/00081—Tubes
-
- 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
- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00162—Controlling or regulating processes controlling the pressure
-
- 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
- Y02P20/50—Improvements relating to the production of bulk chemicals
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Polyamides (AREA)
Abstract
The invention provides a reaction recovery system for continuous synthesis of polyamide, which comprises a multi-stage internal circulation tower reactor and a diamine recovery tower, wherein the reactor is favorable for promoting liquid phase circulation mixing in each stage of reaction unit, and the diamine recovery tower can timely separate and recover diamine components in mixed steam. The whole reaction recovery system has the advantages of high heat exchange efficiency, low energy requirement, low investment and maintenance expenditure of equipment and the like. The invention also provides a continuous synthesis method of polyamide, which synthesizes the polyamide by multi-stage liquid phase circulating mixing and a pressure controllable decreasing mode. By adjusting the gas phase pressure of different reaction stages, the boiling evaporation amount of water and diamine in the liquid phase and the reaction degree of the polyamide salt are effectively controlled, so that the whole polycondensation process is carried out under the trend of gradually decreasing pressure, the coordination and distribution of heat supply amount of different reaction stages are facilitated, the improvement of the polymerization degree of a polyamide product is promoted, the polymerization degree of a final product reaches 10-60, and the requirement of a subsequent pressure reducing device is reduced or eliminated.
Description
Technical Field
The present invention relates to a continuous polymerization process for producing polyamides and to a plant system for carrying out the polymerization process. More specifically, the present invention relates to a continuous synthesis method of polyamide and a reaction recovery system, wherein the system comprises a multi-stage internal circulation tower reactor and a diamine recovery tower.
Background
Methods for the continuous preparation of polyamide materials such as nylon 66 are known in the art, and the classical production scheme comprises 3-5 different reaction vessels connected in series. The processes of evaporation concentration, high-pressure pre-polycondensation, flash evaporation, normal-pressure final polycondensation, vacuum polycondensation and the like are sequentially carried out, the reaction steps are separated spatially, and the reaction container used is usually a tubular reactor or a stirring kettle. The US patent US3402152 discloses a continuous polymerization plant process for nylon 66 invented by monsanto corporation, the main links include concentration, high pressure pre-polycondensation, flash evaporation, normal pressure polycondensation, vacuum polycondensation. The process is the mainstream of the current nylon 66 continuous polymerization process and has the defects of long process, high pre-polycondensation pressure, low reaction efficiency, long flash evaporation depressurization time and the like.
In order to overcome the disadvantages of the conventional continuous production scheme for polyamides, a novel integrated reaction apparatus suitable for the continuous production of polyamide materials is disclosed. U.S. Pat. No. 3,3296217 discloses a falling tube and rectifying tray integrated tower reactor invented by Monsanto; chinese patent CN105745250A discloses a multistage reactor for gas-liquid reverse running of monomer feed with unequal stoichiometric numbers invented by westert technologies; chinese patent CN201210254788.X discloses a gas-liquid reverse integrated tower type reaction device which takes a bi-component monomer as a raw material and comprises a rectification section and a falling film reaction section. The disclosed novel integrated reaction device improves the defects of the traditional polyamide process to a certain extent, simplifies the reaction process and improves the reaction efficiency. However, in order to ensure that the liquid phase flows from the top of the column to the bottom of the column, the gas phase flows in a reverse direction from the bottom of the column and contacts the liquid phase, and the pressure of the whole column is gradually increased from top to bottom, so that the pressure of the gas phase at the inlet of the liquid phase is small, thereby causing risks such as sudden increase of thermal load, large evaporation of diamine, precipitation of unreacted polyamide salt, and the like.
The vertical multi-stage reaction equipment disclosed in the chinese patent CN201910063549.8 has the characteristic of gas-liquid parallel flow, the gas phase pressure at the inlet is high, and the disadvantages of the above integrated equipment are improved to a certain extent, but the device forces most of the gas to continuously flow from top to bottom in order to ensure the bubbling stirring action of the gas in each layer of tray, even additional inert gas is needed to be introduced to ensure the stirring and mixing effect, so that a multi-layer pressure reducing device needs to be equipped to achieve the effect of gradual pressure decrease, the structure is complex, and the pressure drop is relatively uncontrollable.
Disclosure of Invention
In view of these drawbacks of the prior art, it is an object of the present invention to provide a continuous process for the synthesis of polyamides and a multistage internal circulation column reactor.
The technical scheme adopted by the invention is as follows: a reaction recovery system for continuous synthesis of polyamide is characterized by comprising a multistage internal circulation tower reactor, a diamine recovery tower and a diamine recovery storage tank;
the upper part in the reactor of the multistage internal circulation tower reactor is a multistage circulation reaction zone of a first stage, and the lower part is a multistage decompression reaction zone of a second stage;
the multistage circulation reaction zone of the first stage comprises n stages of reaction units, the internal characteristic of spontaneous circulation flow of liquid in each stage of reaction unit and the structural characteristic of liquid phase circulation flow formed by a heat supply zone and a guide cylinder. Each stage of reaction unit comprises a guide shell, a heat supply area formed by a heat exchange tube bundle and a tower tray positioned at the bottom of the reaction unit; the heat supply area is positioned between the guide cylinder and the inner wall of the multistage internal circulation tower reactor; both sides of the upper part of each stage of reaction unit are provided with a liquid phase inlet and a steam outlet; a liquid phase outlet is arranged on the tower tray; the liquid material in the reaction unit is accelerated to move upwards under the combined action of the heating action of the heat supply area and the guiding action of bubbles moving upwards in boiling evaporation, and then flows downwards in a guide cylinder area positioned in the center of the reaction unit, so that the liquid phase integrally forms a circulating flow.
The multistage decompression reaction zone of the second stage comprises m stages of decompression units, each stage of decompression unit is provided with a snakelike decompression pipe, the front m-1 stage of decompression unit also comprises a tower tray, and the tower tray is provided with a liquid phase outlet; each snakelike pressure reducing pipe is connected with a liquid phase outlet of the last stage of pressure reducing unit, and the snakelike pressure reducing pipe of the first stage of pressure reducing unit is connected with a liquid phase outlet of the nth stage of reaction unit in the first stage; the bottom of the m-stage pressure reduction unit is a collecting tank, and one side of the bottom of the m-stage pressure reduction unit is provided with a product outlet. The upper part of each stage of decompression unit is provided with a steam outlet. The snakelike pressure reducing pipe is connected with a tower tray in the last reaction unit in the first stage, and a heat exchange jacket is coated on the outer side of the snakelike pressure reducing pipe;
each vapor outlet is connected to the gas phase inlet of the diamine recovery column through a vapor line for separating and recovering the diamine in the gas phase vapor. Each steam pipeline is provided with a steam valve which can control the gas phase pressure in the reaction unit. A liquid phase outlet of the diamine recovery tower is connected with a diamine recovery storage tank; liquid phase inlets of the 2 nd-nth stage reaction units are used as diamine supplement inlets and are connected with an outlet of a diamine recovery storage tank through a reflux pipeline, and diamine separation products collected from the bottom of a diamine recovery tower are conveyed into the multistage internal circulation tower reactor. A diamine reflux valve is arranged on each reflux pipeline; wherein n and m are positive integers.
Further, n is 2-10, m is 1-5; the diamine recovery tower is a plate-type rectifying tower.
Further, the tray is of a funnel structure, and the inclination angle of the liquid phase outlet from the edge of the tray to the bottom end is not more than 15 degrees.
Further, the ratio of the diameter of the guide shell to the diameter of the multistage internal circulation tower reactor is 0.3: 1 to 0.7: 1.
Further, the diameter of the guide cylinder is gradually increased from top to bottom; wherein, the diameter of the draft tube of the first-stage reaction unit and the diameter ratio of the multistage internal circulation tower reactor are 0.3: 1 to 0.4: 1, the ratio of the diameter of the guide shell of the mth stage reaction unit to the diameter of the multistage internal circulation tower reactor is 0.6: 1 to 0.7: 1.
According to another aspect of the present invention, a continuous synthesis method of polyamide in the above reaction recovery system, comprises: the method comprises the steps of taking a solution containing polyamide salt water as a raw material, introducing the solution into a multistage internal circulation tower reactor from a liquid phase inlet to perform multistage polycondensation reaction in sequence, and controlling gas phase pressure through a steam valve of each stage unit to perform the polycondensation reaction under high pressure, medium pressure and low pressure in sequence. The concentration of the solution comprising polyamide brine is greater than or equal to 30 wt%.
Further, the polyamide salt is selected from any one or more of self-lactam salt, undecamide salt, dodecalactam salt, butanediamine adipate, pentanediamine adipate, hexanediamine terephthalate, hexanediamine sebacate, hexanediamine dodecacarbonate, decanediamine sebacate and dodecadiamine dodecacarbonate;
further, the gas phase pressure of the first-stage reaction is 15atm or more, and the temperature is 200 ℃ to 220 ℃. The gas phase pressure of the last stage reaction is below 6atm, and the temperature is 260-270 ℃.
Further, the gas phase pressure of the first-stage reaction was 16 atm.
The invention has the beneficial effects that: the invention provides a reaction recovery system for continuous synthesis of polyamide, wherein a multistage internal circulation tower reactor contained in the system is favorable for promoting liquid phase circulation mixing in each stage of reaction unit, and a diamine recovery tower can timely separate and recover diamine components in mixed steam. The whole reaction recovery system has the advantages of high heat exchange efficiency, low energy requirement, low investment and maintenance expenditure of equipment and the like. The invention synthesizes polyamide by multi-stage liquid phase circulation mixing and pressure controllable decreasing mode. By adjusting the gas phase pressure of different reaction stages, the boiling evaporation amount of water and diamine in the liquid phase and the reaction degree of the polyamide salt are effectively controlled, so that the whole polycondensation process is carried out under the trend of gradually decreasing pressure, the coordination and distribution of heat supply amount of different reaction stages are facilitated, the improvement of the polymerization degree of a polyamide product is promoted, the polymerization degree of a final product reaches 10-60, and the requirement of a subsequent pressure reducing device is reduced or eliminated.
Drawings
FIG. 1 shows a front view of a multistage internal circulation column reactor of the present invention;
FIG. 2 shows the tray configuration inside the first stage reaction unit of the present invention;
FIG. 3 shows the combination of reaction units with different guide shell sizes in the first stage of the present invention;
FIGS. 4a and 4b show two embodiments of the internal pressure reducing structure of the second-stage reaction unit according to the present invention.
In the figure: a multistage internal circulation column reactor R, a diamine recovery column T, a liquid phase inlet 1, a vapor outlet 2(2a, 2b, 2c, 2d), a reflux diamine inlet 3(3a, 3b, 3c), a product outlet 4, a draft tube 5, a heat supply zone 6, a tray 7, a collection tank 8, a heat exchange tube bundle 9, a liquid phase outlet 10(10a, 10b), a serpentine pressure reducing tube 11, a vapor valve 12(12a, 12b, 12c, 12d, 12e), a vapor line 13(13a, 13b, 13c, 13d, 13e), a line 14, a rectification 15(15a, 15b, 15c, 15d, 15e, 15f, 15g, 15h), a condenser 16, a valve 17, a reboiler 18, a valve 19, a diamine reflux valve 20(20a, 20b, 20c), a serpentine pressure reducing tube inlet 21, a serpentine pressure reducing tube outlet 22, a heat exchange jacket 23, and a valve 24.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
The multistage reaction is realized by a multistage circulation tower reactor containing a two-stage multi-unit and a matched diamine recovery tower as shown in figure 1; wherein the reactor has an inlet 1 for the liquid phase at the top, a vapor outlet 2a, 2b, 2c, 2d or 2e for each stage unit, and a product outlet 4 at the bottom. Wherein a liquid phase inlet 1 is used for injecting a liquid phase stream. The gas discharged from the vapor outlet 2 mainly contains gaseous water and diamine, which are evaporation products in the liquid phase.
The first stage is a multi-stage loop reaction area and comprises n stages of reaction units, each stage of reaction unit comprises a liquid phase circulation loop, and the liquid phase circulation loop comprises a guide shell 5, a heat supply area 6 which is arranged between the inner wall of the reactor and the guide shell and consists of a heat exchange tube bundle 9, and a tower tray 7 which is arranged at the bottom of the reaction unit. The guide shell 5 is superposed with the central axis of the reactor;
the liquid material in the reaction unit is heated in the heating area 6 to raise its temperature and lower its density, and under the action of the bubbles generated by boiling evaporation, the liquid material in the area moves upwards to generate steam. When the gas-liquid mixed fluid rises to the surface of the liquid phase, gas-liquid separation is carried out, wherein the gas overflows from the liquid surface to the gas phase space at the upper part of the reaction unit, and the liquid flows back from the liquid surface into the area of the guide cylinder 5 under the action of gravity and inertia and flows downwards. The liquid phase is circulated between the guide shell and the heating area. The circular flow not only ensures the full mixing of the liquid phase in the reaction unit, but also strengthens the heat exchange efficiency of the heat supply area.
The liquid phase inlet after the first-stage reaction unit is used as a diamine supplement inlet 3. Liquid phase inlets (3a, 3b and 3c) of the 2 nd-nth stage reaction units are connected with an outlet of a diamine recovery storage tank through reflux pipelines, and each reflux pipeline is provided with a diamine reflux valve (20a, 20b and 20 c);
each reaction unit in the first stage is provided with a vapor outlet 2a, 2b, 2c or 2d for discharging a gas mixture overflowing from the liquid phase, each vapor outlet (2a, 2b, 2c, 2d, 2e) is connected to a gas phase inlet of the diamine recovery column through a vapor line, and each vapor line (13a, 13b, 13c, 13d, 13e) is provided with a vapor valve (12a, 12b, 12c, 12d, 12 e). The gas discharged from the vapor outlet is injected into the diamine recovery column T through the vapor valves 12a, 12b, 12c and 12d, the vapor lines 13a, 13b, 13c and 13d and the line 14 in this order. The amount of discharged steam is controlled by a valve, so that the gas phase pressure of the reaction unit is regulated and controlled, and further, the evaporation capacity and the polycondensation reaction are balanced;
the tower tray 7 in each stage of reaction unit is provided with a liquid phase outlet 10 for discharging the liquid phase in the reaction unit to the next reaction unit, and the liquid phase outlet is provided with a valve for controlling the liquid level of the reaction unit where the liquid phase outlet is positioned, thereby regulating and controlling the reaction residence time.
The multistage decompression reaction zone of the second stage comprises m stages of decompression units, each stage of decompression unit is provided with a snakelike decompression pipe 11, a tray 7 is also arranged in the front m-1 stage of decompression unit, and a liquid phase outlet 10 is arranged on the tray 7; each snakelike pressure reducing pipe 11 is connected with the liquid phase outlet 10 of the last stage of pressure reducing unit, and the snakelike pressure reducing pipe 11 of the first stage of pressure reducing unit is connected with the liquid phase outlet 10 of the nth stage of reaction unit of the first stage; the bottom of the m-stage decompression unit is a collecting tank 8, and one side of the bottom of the m-stage decompression unit is provided with a product outlet 4. The upper part of each stage of decompression unit is provided with a steam outlet 2. The pressure reduction unit shown in the figure only has one stage comprising a serpentine pressure reduction pipe 11 and a collecting tank 8 positioned below the serpentine pressure reduction pipe and used for collecting products, wherein the serpentine pressure reduction pipe 11 is connected with a liquid phase outlet of a tray 7d in the last reaction unit in the first stage, and the outer side of the serpentine pressure reduction pipe 11 is coated with a heat exchange jacket 23; the liquid phase substance enters the serpentine pressure reduction pipe 11 through a liquid phase outlet in the last reaction unit in the first stage, after pressure reduction, the liquid flowing out of the serpentine pressure reduction pipe outlet enters a reactor bottom collecting tank 8, and the gas is discharged from a steam outlet 2 e.
The diamine recovery column T may be any suitable rectification column. The diamine recovery column illustrated in the figure contains eight rectification trays 15a-15h, which may be sieve trays or bubble cap trays and may be not limited in number to eight, and may be more or less than eight. The trays can also be replaced by packing that performs the separation function, including raschig rings, pall rings, glass beads, glass wool, structured packing, or any other suitable packing material. The column may have any suitable height, such as from 1m to 20m, and the column may have any suitable diameter, such as from about 0.1m to 10 m.
The mixed steam is injected into a diamine recovery tower, gradually moves upwards, passes through 8 rectification tower plates, is discharged above 15a, is condensed into liquid by a condenser 16, then one part of the liquid is discharged through a valve 17, and the other part of the liquid flows back to the tower. The amount of reflux can be controlled by parameters such as temperature, flow rate of the heat exchange fluid through the condenser, and the operating pressure within the column. A part of the liquid at the bottom of the column can be converted into gas flowing upward by heating in the reboiler 18, and the other part of the liquid is discharged through the valve 19, in which case the liquid phase contains almost all diamine as a component. The diamine thus separated flows into a diamine recovery tank through a liquid phase outlet, and the recovered diamine is quantitatively injected into all the reaction units except the first reaction unit in the first reaction stage from diamine reflux inlets 3a, 3b and 3c directly or together with the diamine injected into the diamine recovery tank from the outside through reflux valves 20a, 20b and 20c, and used for supplementing the diamine in the reaction liquid phase to ensure the balance between the terminal carboxyl groups and the terminal amine groups of the polyamide product.
The polyamide salt solution is injected under pressure from the liquid phase inlet 1 into the first reaction unit of the multistage circulation column reactor. Suitable polyamide salt solutions have a concentration of not less than 30 wt%, preferably at least 50 wt%. The polyamide salt solution continuously enters the tray 7 and gradually accumulates until the guide shell and the heating tube bundle are completely immersed in the liquid. With the continuous heating of the polyamide salt solution by the heating zone 6, the density difference and the upward bubbling of the gas bubbles together cause the liquid to form a spontaneous circulation flow in the reaction unit, and the water in the liquid phase and part of the diamine molecules are continuously evaporated and converted into gas during the circulation heating process, and meanwhile, the polyamide salt is continuously polycondensed to produce polymer and water. The gas generated by the reaction is discharged from the vapor outlet 2a, and the reaction liquid is discharged from the liquid phase outlet 10 at the center of the tray and enters the next reaction unit with lower pressure for the second stage reaction. Similarly to the first stage, the liquid in the second stage also circulates spontaneously on the tray between the draft tube and the heating zone and undergoes polycondensation simultaneously. The gas phase pressure in the reaction unit is regulated and controlled by controlling a valve of a second-stage steam outlet 2b, and in addition, a liquid phase stream mainly containing diamine, which is obtained by recovering water and diamine mixed steam generated in the reaction process discharged from a higher-stage reaction unit through a diamine recovery tower T, returns to the reaction system through a reflux diamine inlet 3a arranged in the second reaction unit for supplementation. The liquid in the second reaction unit enters the subsequent repeated structural unit once after internal circulation reaction to carry out polycondensation reaction. After the reaction of the first stage, the operation pressure of the system is reduced to 6-12atm, then the liquid flowing out from the last reaction unit of the first stage enters the snake-shaped pressure reducer 11 of the second reaction stage connected with the liquid for pressure reduction, the gas-liquid mixture rapidly reduces the pressure through the tubular pressure reduction unit and finally reaches a low pressure or normal pressure state, and the steam generated in the pressure reduction process is injected into the diamine recovery tower T through the pipeline 14 together with the steam discharged from the reaction unit of the first stage through the steam outlet 2e, the valve 12e and the pipeline 13e in sequence to carry out gas separation and diamine recovery. The liquid product after the pressure reduction is collected in a polymer collection tank 8 at the bottom of the reactor, and an acceptable polymer product is discharged from the polyamide material outlet 4.
Preferably, the number of the first-stage reaction units is 2-10, the number of the second-stage decompression units is 1-5, and the polymerization degree of the product can be effectively controlled by regulating and controlling the number of the reaction layers of the two stages so as to adapt to the production requirements of polyamide materials with different performances.
The tray has a funnel configuration with a slope angle from the edge to the outlet of no more than 15 degrees.
The diameter ratio of the guide shell to the reactor is 0.3: 1 to 0.7: 1.
The heating tube bundles in the heat supply area are arranged in various ways, and are arranged in a rectangular way or a triangular way or other ways meeting the heat supply quantity.
Fig. 2 shows the tray configuration inside the first stage reaction unit of the present invention. The liquid material flowing in from the upper layer circulation reaction unit is injected into the reaction unit through a valve 24, and a part of diamine separated and recovered from the diamine recovery tower T enters the reaction unit through a reflux diamine inlet 3 to supplement the diamine content in the reaction system. The liquid in the heat supply area 6 in the reaction unit is heated and boiled under the heating action of the heat exchange tube bundle 9 to generate a large amount of steam, and the steam moves upwards in a bubble form to induce the liquid material to flow upwards along with the steam. And the gas-liquid mixture is subjected to gas-liquid separation when rising to the surface of a liquid phase, wherein gas overflows from the liquid surface to a gas phase space at the upper part of the reaction unit, and the liquid flows back from the liquid surface into the area of the guide cylinder 5 under the action of gravity and inertia and flows downwards. The liquid phase is circulated between the guide shell and the heating area. The circular flow not only ensures the full mixing of the liquid phase in the reaction unit, but also strengthens the heat exchange efficiency of the heat supply area. In addition, the speed of the circulating flow is affected by the combined action of the evaporation capacity and the channel size, so that the strength of the circulating flow can be regulated and controlled by changing the size of the guide shell 5 or the heat supply capacity of the heat supply area 6. The whole generated by the reaction is discharged through a steam outlet 2, and the reaction materials are discharged from a liquid phase outlet 10 at the bottom and enter the next layer of reaction unit.
FIG. 3 shows the combination of reaction units with different guide shell sizes in the first stage of the present invention. In the figure, the diameter of the guide shell 5 in the reaction unit is gradually increased from top to bottom, and the volume of the heat supply area 6 is gradually reduced. The salt solution flows through each circulation reaction unit from top to bottom in sequence, the water content of the solution at the early stage of the reaction is high, and meanwhile, the water generated by the polycondensation reaction is more, so that more heat needs to be provided to remove small molecular components in a reaction system, and meanwhile, the temperature of reaction materials is maintained, so that more heat exchange tube bundles and a larger heating area are needed. In addition, the width of the guide shell 5at the early stage of the reaction is relatively narrow, so that the circulating flow rate is relatively high, and the overall heat exchange efficiency is further improved. The water content in the reaction materials is reduced in the middle and later stages of the reaction, the requirement on the heat supply is not high in the early stage, so that the size of the guide cylinder of the lower reaction unit is widened, the volume of the heating area is reduced, and the circular flow and the reaction of the liquid phase materials in the reaction units are more stable. Wherein, preferably, the ratio of the diameter of the guide shell 5 of the first-stage reaction unit to the diameter of the multistage internal circulation tower reactor is 0.3: 1, the ratio of the diameter of the guide shell 5 of the mth stage reaction unit to the diameter of the multistage internal circulation tower reactor is 0.6: 1.
FIGS. 4a and 4b show two embodiments of the internal pressure reducing structure of the second-stage reaction unit according to the present invention. Snakelike decompression pipe 11 comprises the diameter along with the crooked pipeline of tube side crescent, and snakelike decompression pipe 11 outside parcel has heat exchange jacket 23 to guarantee the temperature of reaction material. The liquid material flowing from the first-stage reaction unit enters the snake-shaped pressure reduction pipe 11, the system pressure is rapidly reduced along with the increase of the pipe pass, the small molecular components are rapidly evaporated to consume a large amount of heat, and meanwhile, the liquid-phase reactant continuously becomes viscous. The serpentine shaped pressure reduction duct 11 provides two different embodiment variations, depending on the mounting, the serpentine shaped pressure reduction duct 11 in fig. 4a being arranged horizontally and the serpentine shaped pressure reduction duct 11 in fig. 4b being arranged vertically.
The invention also provides a continuous synthesis method of polyamide, which comprises the following steps: the polyamide is synthesized by a multistage polycondensation reaction using a solution containing a polyamide salt solution as a raw material. Boiling evaporation capacity of water and diamine in a liquid phase and condensation polymerization degree of polyamide salt can be regulated and controlled by controlling gas phase pressure of each stage of reaction unit in the first stage, the whole condensation polymerization process is carried out under the trend that pressure gradually decreases, heat supply in different reaction stages is favorably coordinated and distributed, the promotion of polymerization degree of polyamide products is promoted, residual moisture in a reaction system is rapidly evaporated from pressure of the reaction system to normal pressure in the second stage, the molecular weight of a polymer is rapidly increased, the polymerization degree of a final product reaches 10-60, and the defects that heat supply distribution is unbalanced and the molecular weight of the polyamide products is uncontrollable are effectively overcome. Specific examples are provided below to further illustrate the methods and systems of the present invention.
Example 1
The nylon 66 saline solution with the temperature of 215 ℃ and the concentration of 69wt percent is injected into the multi-stage internal circulation tower reactor, the temperature of the first stage reaction unit of the first stage of the reaction is controlled at 216 ℃, and the pressure is controlled at 16atm by a steam outlet valve. The reaction materials pass through 6 stages of reaction units, and the ratio of the diameter of the guide shell of each stage of reaction unit to the diameter of the tower is 0.3: 1. 0.35: 1. 0.4: 1. 0.5: 1. 0.6: 1 and 0.7: 1, gradually raising the operating temperature to 230 ℃ and reducing the pressure to 12 atm. The reaction mass was injected into the second stage consisting of 2 sets of pressure reducing units comprising horizontally arranged serpentine pressure reducing tubes, the operating temperature was gradually raised from 238 ℃ to 260 ℃ and the operating pressure was reduced to 6 atm. The diamine recovery tower adopts plate-type rectifying tower equipment, the total tower has 8 layers of tower plates, the reflux ratio of condensed water at the top of the tower is 0.16, and the recovered hexamethylene diamine material is as follows: 2: 1.5: 1: the ratio of 1 is injected into the 2 nd to 6 th reaction units of the first stage, respectively. The reaction residence time of the whole tower is controlled to be 50min, and finally the nylon 66 melt material with the polymerization degree of 33 is obtained.
Example 2
The nylon 66 saline solution with the temperature of 200 ℃ and the concentration of 60wt percent is injected into a multi-stage internal circulation tower reactor, the temperature of a first layer reaction unit in the first stage of reaction is controlled at 216 ℃, and the pressure is 15 atm. The reaction materials pass through 7 layers of circulating reaction units, and the ratio of the diameter of the guide shell of each stage of reaction unit to the diameter of the tower is 0.3: 1. 0.35: 1. 0.4: 1. 0.45: 1. 0.5: 1. 0.6: 1 and 0.7: 1, gradually raising the operating temperature to 232 ℃ and reducing the pressure to 11 atm. The reaction materials are injected into the second stage for continuous reaction, the second stage consists of 2 pressure reducing units comprising serpentine pressure reducing pipes which are vertically arranged, the operating temperature is gradually increased from 236 ℃ to 260 ℃, and the operating pressure is reduced to 2 atm. The diamine recovery tower adopts plate-type rectifying tower equipment, the total tower has 10 layers of tower plates, the reflux ratio of condensed water at the top of the tower is 0.15, and the mass of the recovered hexamethylene diamine material is 2: 2: 1.5: 1.5: 1: the ratio of 1 was injected into the 2 nd to 7 th reaction units of the first stage, respectively. The reaction residence time of the whole tower is controlled to be 62min, and finally the nylon 66 melt material with the polymerization degree of 39 is obtained.
Example 3
The nylon 66 saline solution with the temperature of 220 ℃ and the concentration of 70 weight percent is injected into the multi-stage internal circulation tower reactor, the temperature of the first stage reaction unit of the first stage of the reaction is controlled at 216 ℃, and the pressure is controlled at 16atm by a steam outlet valve. The reaction materials pass through 2 stages of reaction units, and the ratio of the diameter of the guide shell of each stage of reaction unit to the diameter of the tower is 0.3: 1 and 0.7: 1, gradually raising the operating temperature to 230 ℃ and reducing the pressure to 12 atm. The reaction mass is injected into the second stage to continue the reaction, the second stage is composed of 5 groups of pressure reducing units comprising horizontally arranged serpentine pressure reducing pipes, the operating temperature is gradually increased from 235 ℃ to 265 ℃, and the operating pressure is reduced to 1 atm. The diamine recovery tower adopts plate-type rectifying tower equipment, the total tower has 7 layers of tower plates, the reflux ratio of condensed water at the top of the tower is 0.19, and the recovered hexamethylene diamine material is injected into the 2 nd reaction unit of the first stage. The reaction residence time of the whole tower is controlled to be 39min, and finally the nylon 66 melt material with the polymerization degree of 42 is obtained.
Example 4
The temperature of 215 ℃ and 70 wt% nylon (66-co-6T) saline solution are injected into a multi-stage internal circulation tower reactor, the temperature of a first stage reaction unit in the first stage of the reaction is controlled at 220 ℃, and the pressure is controlled to be 16atm through a steam outlet valve. The reaction materials pass through 10 stages of reaction units, and the ratio of the diameter of the guide shell of each stage of reaction unit to the diameter of the tower is 0.3: 1. 0.33: 1. 0.35: 1. 0.37: 1. 0.4: 1. 0.45: 1. 0.47: 1. 0.5: 1. 0.6: 1. and 0.7: 1, gradually raising the operating temperature to 245 ℃ and reducing the pressure to 11 atm. The reaction mass was injected into the second stage, which was 1 set of decompression units comprising horizontally arranged serpentine decompression tubes, and the operating temperature was gradually raised from 245 ℃ to 270 ℃ and the operating pressure was lowered to 1.5 atm. The diamine recovery tower adopts plate-type rectifying tower equipment, the total tower has 10 layers of tower plates, the reflux ratio of condensed water at the top of the tower is 0.21, and the mass of the recovered hexamethylene diamine material is 2: 2: 2: 1.5: 1.5: 1.5: 1: 1: the ratio of 1 is injected into the 2 nd to 10 th reaction units of the first stage, respectively. The reaction residence time of the whole column is controlled to be 78min, and finally the melt material of nylon (66-co-6T) with the polymerization degree of 51 is obtained.
Claims (9)
1. A reaction recovery system for continuous synthesis of polyamide is characterized by comprising a multistage internal circulation tower reactor, a diamine recovery tower and a diamine recovery storage tank, wherein the upper part in the multistage internal circulation tower reactor is a multistage circulation reaction zone of a first stage, and the lower part in the multistage internal circulation tower reactor is a multistage decompression reaction zone of a second stage;
the multistage circulation reaction zone of the first stage comprises n stages of reaction units, and each stage of reaction unit comprises a guide shell (5), a heat supply zone (6) formed by a heat exchange tube bundle (9) and a tower tray (7) positioned at the bottom of the reaction unit; the heat supply area (6) is positioned between the guide shell (5) and the inner wall of the multi-stage internal circulation tower reactor; both sides of the upper part of each stage of reaction unit are provided with a liquid phase inlet and a steam outlet (2); a liquid phase outlet (10) is arranged on the tray (7);
the multistage decompression reaction zone of the second stage comprises m stages of decompression units, each stage of decompression unit is provided with a snakelike decompression pipe (11), the front m-1 stage of decompression unit also comprises a tower tray (7), and the tower tray (7) is provided with a liquid phase outlet (10); each snakelike pressure reducing pipe (11) is connected with a liquid phase outlet (10) of the last stage of pressure reducing unit, and the snakelike pressure reducing pipe (11) of the first stage of pressure reducing unit is connected with the liquid phase outlet (10) of the nth stage of reaction unit in the first stage; the bottom of the m-stage decompression unit is a collecting tank (8), and a product outlet (4) is arranged on one side of the bottom; the upper part of each stage of decompression unit is provided with a steam outlet (2);
each steam outlet is connected with a gas phase inlet of the diamine recovery tower through a steam pipeline, and each steam pipeline is provided with a steam valve; a liquid phase outlet of the diamine recovery tower is connected with a diamine recovery storage tank; liquid phase inlets of the 2 nd-nth stage reaction units are connected with an outlet of a diamine recovery storage tank through backflow pipelines, and a diamine backflow valve is arranged on each backflow pipeline; wherein n and m are positive integers.
2. The reaction recovery system of claim 1, wherein n is 2 to 10 and m is 1 to 5; the diamine recovery tower is a plate-type rectifying tower.
3. The reaction recovery system according to claim 1, wherein said tray (7) is of a funnel structure, and the inclination angle of the liquid phase outlet from the edge of the tray to the bottom end is not more than 15 degrees.
4. The reaction recovery system according to claim 1, wherein the ratio of the diameter of the draft tube (5) to the diameter of the multistage internal circulation column reactor is in the range of 0.3: 1 to 0.7: 1.
5. The reaction recovery system according to claim 4, wherein the diameter of the draft tube (5) is gradually increased from top to bottom; wherein the ratio of the diameter of the guide shell (5) of the first-stage reaction unit to the diameter of the multistage internal circulation tower reactor is 0.3: 1 to 0.4: 1, the ratio of the diameter of a guide shell (5) of the nth stage reaction unit to the diameter of the multistage internal circulation tower reactor is 0.6: 1 to 0.7: 1.
6. A continuous process for the synthesis of a polyamide according to the reaction recovery system of any one of claims 1 to 5, characterized in that it comprises: introducing a solution containing polyamide salt water as a raw material from a liquid phase inlet (1) into a multistage internal circulation tower reactor to perform multistage polycondensation reaction in sequence, and controlling gas phase pressure through a steam valve of each stage unit to perform polycondensation reaction under high pressure, medium pressure and low pressure in sequence; the concentration of the solution comprising polyamide brine is greater than or equal to 30 wt%.
7. The method of claim 6, wherein the polyamide salt is selected from any one or more of caprolactam salt, undecanolactam salt, dodecalactam salt, butanediamine adipate, pentanediamine adipate, hexanediamine terephthalate, hexanediamine sebacate, hexanediamine dodecacarbonate, decanediamine sebacate, and dodecadiamine dodecacarbonate.
8. The method as claimed in claim 6, wherein the gas phase pressure of the first stage reaction is 15atm or more, and the temperature is 200 ℃ to 220 ℃; the gas phase pressure of the last stage reaction is below 6atm, and the temperature is 260-270 ℃.
9. The method of claim 8, wherein the gas phase pressure of the first stage reaction is 16 atm.
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