CN113769423A - Cyclic supplement type devolatilization device and process - Google Patents
Cyclic supplement type devolatilization device and process Download PDFInfo
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Abstract
The invention discloses a cyclic supplement type devolatilization device, which at least comprises a first-stage devolatilization device, a second-stage devolatilization device and a circulating supplement type devolatilization device, wherein the first-stage devolatilization device comprises a melt pump, a preheater and a devolatilization tank which are sequentially connected in series; the devolatilization tank is provided with a split-flow melt pump at the outlet, and the split-flow melt pump is connected with the inlet of the preheater to form a circulation passage between the preheater and the devolatilization tank. The invention adopts a mode of circularly supplementing flow, can increase the operation elasticity of the devolatilization device aiming at the polymer which can not form stable flow in small-batch production, can adjust the flow in a pipeline according to the production requirement, makes up the defects of flow breaking, dry plate and the like caused by insufficient flow, and reduces the loss of materials.
Description
Technical Field
The invention relates to the technical field of devolatilization of high-viscosity fluid, in particular to a multistage series high-viscosity fluid devolatilization device and a process thereof.
Background
The devolatilization is a technology for removing one or more monomers or solvents which do not participate in the reaction from the polymer through heating and volatilization, and the devolatilization process needs to consider effective heating to increase the heating temperature so as to volatilize the monomers and the solvents and simultaneously heat the polymer to be above the softening point and have fluidity, but simultaneously the devolatilization process is not overheated and does not damage the properties of the polymer such as molecular weight, color and the like. Obviously, the devolatilization process of the polymer is essentially a process of melting the polymer by heating and controlling the separation, and the main key points of the devolatilization process are the control of the pressure and the temperature as well as the heating time. In the prior art, multi-stage operation is mostly adopted, and generally, a multi-stage devolatilization tank is used together to gradually remove volatile substances in polymers, so that high-purity polymers are realized. However, the combination of the multi-stage devolatilization tanks needs to face the problem that the properties of the polymer are influenced by the long heating time, so that the devolatilization technology needs to comprehensively consider the economic benefit and the practicability of the process, the higher the number of stages is, the higher the cost is, and the influence of the overlong heating time on the properties of the polymer is.
However, for polymers with high viscosity, volatile substances therein are affected by mass transfer resistance due to the physical properties of the polymers, and cannot be removed, and the principle conversion rate of the polymers is generally 40-60%, wherein the polymers contain a large amount of unreacted raw materials and various reagents added in the polymerization process, so that the final impurity components are very high, and the properties of the polymers are affected.
Chinese patent CN112933665A provides a devolatilization system and a devolatilization method for high viscosity fluid, which uses an atomization separator to remove gas impurities in the fluid, uses the interaction between high speed gas and high viscosity fluid to atomize, forms fog drops and volatile components, and the fog drops fall and are re-aggregated into high viscosity fluid, thereby removing the volatile components therein. However, the method changes the physical properties of the polymer after atomization and reaggregation, and meanwhile, the atomization method only has a good removal effect on volatile small-molecular organic matters, the removal effect of other components is not good, fog drops are formed with the polymer at the same time, the physical effect is generated in the reaggregation process, and impurities cannot be removed from the high-viscosity polymer fluid while the properties of the polymer are influenced.
On the other hand, with the development of the chemical industry, a large number of products with high added value and small market demand are available, such as leveling agents, dispersing agents, adhesion promoters and the like in the coating industry, and the products have outstanding performance, but the added amount is small but the price is high, taking the organosilicon promoters as an example, the price per kilogram is 400-600 yuan, so the products are usually produced in small batches in the processing process, the processing of the products by adopting the existing large-scale processing equipment is greatly limited, and meanwhile, due to the fact that the flow in a pipeline is too low, the flow is cut off in a devolatilization tank, a liquid film of a polymer is dried, the devolatilization efficiency is reduced, volatile impurities cannot be completely removed in the devolatilization process, and the quality of the products is affected.
Disclosure of Invention
The invention aims to provide a cyclic supplement type devolatilization device and a cyclic supplement type devolatilization process, which can realize high devolatilization efficiency by simple and low modification on the basis of the conventional devolatilization device and have the advantages of low cost, no influence of the devolatilization process on the physical properties of polymers and the like.
In order to achieve the purpose of the invention, the technical scheme of the invention is as follows:
a cyclic supplement type devolatilization device at least comprises a first-stage devolatilization device, which comprises a melt pump, a preheater and a devolatilization tank which are sequentially connected in series;
the devolatilization tank is provided with a split-flow melt pump at the outlet, the split-flow melt pump is connected with the inlet of the preheater, and the preheater and the devolatilization tank form a circulation passage.
In a preferred embodiment, the preheater and the devolatilizer are of unitary construction without a tubular connection, the bottom of the preheater being secured to the top of the devolatilizer and extending axially through the devolatilizer into the tank, and the fluid flowing through the preheater directly into the devolatilizer.
As a preferred embodiment, the preheater is a single-pass tubular heat exchanger, and the inner wall of the tubular heat exchanger is provided with a raised pattern structure to increase the surface area of the inner wall of the tubular heat exchanger and increase the contact area and residence time of the tube pass of the fluid.
In a preferred embodiment, the preheater is a single pass tubular heat exchanger with static mixing elements radially disposed within the tubes.
In a preferred embodiment, a falling film evaporator is arranged in the devolatilization tank, and the falling film evaporator comprises a distribution disc and a falling film element, wherein a plurality of film distribution holes are regularly arranged on the distribution disc, and fluid flows onto the distribution disc through the preheater and is uniformly distributed through the film distribution holes to form a uniform falling film through the falling film element. In a preferred embodiment, the devolatilizer can be used in a plurality of stages, and the outlet of the last devolatilizer is connected to the inlet of the preheater of any stage to form a circulation path.
As a preferred embodiment, the devolatilization device is connected with the preheater through a return line, and at least one preheater is arranged on the return line.
In a preferred embodiment, the melt pump is connected to the preheater through a flow line, and a static mixer is disposed on the flow line to uniformly mix the fluids in different lines.
As another object of the invention, the invention adopts another technical scheme, and the process for devolatilizing the polymer by adopting the circulating complementary type devolatilization device comprises the following steps:
(1) the melt pump delivers fluid to the preheater;
(2) the fluid flows to the distribution disc through the preheater and forms a falling film through the film distribution holes on the distribution disc;
(3) the fluid flows to a liquid storage area of the devolatilization tank under the action of self gravity;
(4) shunting the devolatilized fluid as required, adjusting an inlet valve of the preheater, adjusting the flow of the valve according to the reflux ratio, and completely or partially refluxing the fluid to the inlet of the preheater for devolatilization again;
(5) the fluid which is not refluxed in the step (4) flows into a collecting device after being detected to be qualified; the unqualified products flow back to the preheater again and are devolatilized again.
Further, in the step (5), when the fluid is unqualified in detection, the fluid can flow back to the preheater again to be devolatilized again, and the fluid can be circulated for multiple times until the fluid is qualified in detection and finally collected.
In the prior art, polymer products with high added value are often high in quality required in the production process, and the market demand is not so large because of small addition amount, so that a production party keeps small-scale production. Because the output is small, when entering the devolatilization stage, the flow rate of the fluid in the pipeline needs to be kept at a stable value so as to ensure that a liquid film formed in the devolatilization tank cannot generate a fault, and therefore, a low flow rate inflow can be maintained. If the flow rate is reduced during the devolatilization process, the falling film flow rate is not stabilized and will accumulate on the falling film elements within the devolatilization tank to form a dry plate. When the flow rate is restored again, the dry plate part can not form a film again, so that a complete film can not be formed in the subsequent falling film. On one hand, the method causes great waste of materials, reduces the product conversion rate of the whole polymerization reaction, and on the other hand, influences the efficiency of the devolatilization process.
The invention adopts a circulation supplement method, when the flow rate needs to be reduced, the fluid which is subjected to the first-stage devolatilization is circulated into the preheater again through the melt pump, and the reduced flow is compensated by adjusting the reflux ratio, so that the flow entering the preheater part is kept stable, the fault phenomenon is avoided, and the completeness of the falling film is maintained.
On the other hand, for the polymer which is required to be high or has high viscosity and is difficult to devolatilize, complete devolatilization is realized through primary devolatilization or secondary devolatilization, and for the polymer which is detected to be unqualified, the polymer can flow back to the preheater again through the circulating system, and devolatilization is carried out again, and the polymer can be circulated for multiple times until the polymer meets the requirement.
By adopting the technical scheme, the invention achieves the following technical effects:
1. the invention adopts a mode of circularly supplementing flow, can increase the operation elasticity of the devolatilization device aiming at the polymer which can not form stable flow in small-batch production, can adjust the flow in a pipeline according to the production requirement, makes up the defects of flow breaking, dry plate and the like caused by insufficient flow, and reduces the loss of materials.
2. Aiming at high-viscosity polymers, the devolatilization process is difficult to devolatilize, and even after multi-stage devolatilization, the content of small molecules still cannot meet the requirement, the polymer which is devolatilized is refluxed into a preheater again to be devolatilized again by adopting the cyclic devolatilization process, so that the loss is avoided.
3. The method can be realized only by simply modifying the devolatilization device, does not influence the continuous use of the original devolatilization process, has wide application range and greatly saves resources and cost.
Drawings
FIG. 1 is a flow diagram of a one-stage series devolatilization apparatus of examples 1 and 2 of this invention.
FIG. 2 is a flow chart of a two-stage devolatilization apparatus of example 3 of the present invention.
Fig. 3 is a schematic structural view of the hollow overpass disc of the present invention.
Reference numerals: 1, a melt pump; 2, a preheater; 201 tubes; 202 a three-dimensional curved sheet; 3, devolatilizing tank; 301 a distribution tray; 302 heat-preserving jacket; 303 a stripping agent input port; 4 flow valve; 5a circulation pipeline; 501 a static mixer; 6 a first-level melt pump; 7, a primary preheater; 8, a first-stage devolatilization tank; 9 a secondary melt pump 10 a secondary preheater; 11 a secondary devolatilization tank; 12 split melt pumps; 13 primary flow valve; 14 secondary flow valve; 15 a return line; 1501 a heat exchanger.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the specific contents of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a supplementary circulating devolatilization device, which at least comprises a primary devolatilization device. The first-stage devolatilization device comprises a first melt pump, a preheater and a devolatilization tank which are sequentially connected in series; wherein, the outlet of the devolatilization tank is provided with a second melt pump, and the second melt pump is connected with the inlet of the preheater, so that the preheater and the devolatilization tank form a circulation passage. The circulation path enables the devolatilized product to be returned to the preheater again for devolatilization. The devolatilization process adopting the devolatilization device comprises the following steps:
(1) the first melt pump delivers fluid to the preheater;
(2) the fluid flows to the distribution disc through the preheater and forms a falling film through the film distribution holes on the distribution disc;
(3) the fluid flows to a liquid storage area of the devolatilization tank under the action of self gravity;
(4) setting a reflux ratio, adjusting an inlet valve of the preheater, adjusting the flow of the valve according to the reflux ratio, simultaneously adjusting a valve at the bottom of the devolatilization tank, mixing the devolatilized fluid with the fluid which is not devolatilized through a circulation pipeline by a second melt pump, and then refluxing the devolatilized fluid into the preheater, wherein all or part of the devolatilized fluid reflows to an inlet of the preheater to supplement the flow of the fluid in the preheater;
(5) and (4) the fluid after devolatilization in the step (4) flows into the collecting device after being detected to be qualified, can flow back to the preheater again when being detected to be unqualified, is devolatilized again, can be circulated for multiple times until being detected to be qualified, and is finally collected.
Further analysis is described below in connection with specific examples.
Example 1
In the embodiment, a high-viscosity fluid is taken as an example, and specifically includes but is not limited to SAN resin, polymethyl methacrylate, polyacrylonitrile and the like, the devolatilization of the high-viscosity fluid is characterized in that bubbles are more during the devolatilization but are not easy to be completely removed, the updating rate of the fluid surface is improved by increasing the flow rate of the fluid, but the method can cause the fluid to stay in the devolatilization tank for too short time and cannot be fully devolatilized, so that the high-efficiency devolatilization can be realized by only using a single-stage devolatilization unit in an increased circulation manner.
This embodiment is including melt pump 1, pre-heater 2 and the devolatilization jar 3 of establishing ties in proper order, and melt pump 1 and pre-heater 2 pass through circulation pipeline 5 and connect, and pre-heater 2 is fixed on the top of devolatilization jar 3, forms an overall structure. The preheater 2 is a tubular heat exchanger, a plurality of single-pass tubes 201 are uniformly arranged inside the tubular heat exchanger, static mixing elements are respectively arranged in the tubes, preferably, the static mixing elements adopt hollow cross-over disc inner members which are tubular structures, a corrugated structure is arranged on the near wall of the inner wall in each tube, the flow condition is improved by alternately exchanging the fluid in the near wall region and part of the fluid in the central region, the turbulence degree of the near wall region can be improved, radial mixing is promoted, the damage of a boundary layer of the polymer fluid in the preheater is reduced, the thermal resistance is reduced, the radial temperature and the concentration uniformity are improved, the section of the fluid is rapidly changed, the fluid can be rapidly mixed and preheated, the working efficiency of the preheater is improved, and the energy consumption is reduced. Referring to fig. 3, a plurality of V-shaped three-dimensional curved sheets 202 connected end to end are arranged in the inner wall of the tube array 201 to form a hollow overpass structure. The upper end and the lower end of the three-dimensional curved surface sheet 202 are in arc-shaped alternate connection, fluid flows close to the inner wall in the radial direction, the included angle between the speed of the inner wall and the temperature gradient is reduced, heat transfer is promoted, dead zone parts of materials are avoided, and efficient heat exchange is achieved.
A distribution plate 301 and a falling film element are arranged in the devolatilization tank 3. A plurality of shell tubes of pre-heater 2 are fixed in the bottom opening of devolatilization jar 3 to with distribution disc 301 lug connection, make fluid directly carry to devolatilization jar 3 on distribution disc 301 after the heat transfer of pre-heater 2, a plurality of cloth membrane hole has evenly been arranged on distribution disc 301, can be with fluid evenly distributed to falling liquid film component on, fluid relies on self action of gravity to form even falling liquid film flow on falling liquid film component, volatile composition forms the bubble on falling liquid film surface, breaks away from the fluid, realizes the devolatilization.
The shell of the devolatilization tank 3 is provided with a heat preservation jacket 302 to reduce heat loss, and the upper part and the lower part of the heat preservation jacket 302 are respectively provided with a heating medium inlet and a heating medium outlet. The top of the devolatilization tank 3 is provided with a volatile matter outlet, and the volatile matters removed by the devolatilization tank 3 are recovered through the outlet and reused.
The bottom of devolatilization jar 3 is equipped with stripping agent input port 303, can add the stripping agent through stripping agent input port 303, and the stripping agent can be steam or other inert gas, can reduce the partial pressure of volatile, improves volatile diffusion coefficient, shortens the time of starting to run, and the bubble is in advance, strengthens the mass transfer, improves devolatilization efficiency, and the stripping agent can drive the export of little subtotal gas from volatile gas together and discharge.
The bottom outlet of devolatilizing tank 3 is equipped with reposition of redundant personnel melt pump 12, and reposition of redundant personnel melt pump 12 is connected with collection device and circulation pipeline 5 respectively, and reposition of redundant personnel melt pump 12 passes through return line 15 with circulation pipeline 5 to be connected, and the link B of circulation pipeline 5 is equipped with the valve, can open the valve according to the particular case of production and form circulation route. Be equipped with heat exchanger 1501 on return line 15, when the fluid flow after the devolatilization is to preheater 2, in order to avoid the flow overlength, the fluid cooling takes place to solidify, consequently is equipped with heat exchanger 1501 on return line 15 and preheats the fluid, avoids solidifying the jam pipeline.
Specifically, the split-flow melt pump 12 and the connecting end B are arranged between the melt pump 1 and the preheater 2, and the flow valve 4 is arranged between the connecting end B and the melt pump 1. That is, the devolatilization device can form a circulation structure, after the first devolatilization, the fluid at the outlet of the split-flow melt pump 12 passes through the detector to determine whether the content of the volatile component meets the requirement, and directly enters the collection device after meeting the requirement, and if not, the valve of the connecting end B can be opened again and the flow of the flow valve 4 can be adjusted, so that the sum of the flow of the refluxed devolatilized fluid and the flow in the pipeline is equal to the flow of the fluid in the original pipeline, thereby ensuring the stability of the flow, and ensuring the stable falling film of the demolding element in the devolatilization tank to enter for the second devolatilization. If the secondary devolatilization still does not meet the requirements, the reflux ratio can be adjusted again according to the operation for cyclic devolatilization.
The SAN resin devolatilization process specifically comprises the following steps:
(1) the fluid is conveyed to a preheater 2 through a melt pump 1, and the fluid is mixed and preheated in the preheater 2;
(2) the fluid flows into the devolatilization tank 3 after being preheated, a falling film is formed by a distribution disc 301 and a falling film element in the devolatilization tank 3, the first devolatilization is carried out, and the devolatilization completed fluid flows into a liquid storage area of the devolatilization tank;
(3) opening a valve at the bottom of the devolatilization tank, and sampling to detect the devolatilization rate of the fluid; the qualified fluid is conveyed to a collecting device through a separation melt pump 12;
(4) unqualified fluid flows through the return line 15 to the connecting end B and flows back to the preheater 2, devolatilizes again, and the process is circulated for many times until qualified.
Preferably, during the beginning of the devolatilization process in the devolatilization tank 3 of step (2), a stripping agent, which may be steam or other inert gas, may be introduced through the stripping agent inlet 303.
Specifically, 75 wt% of SAN resin and dichloroethylene serving as a solvent enter a preheater through a flow pipeline, are preheated to 250-280 ℃, enter a devolatilization tank 3 for devolatilization after being decompressed by an adjusting valve, the temperature in the tank is 200-240 ℃, the operation pressure is 250-800 Pa, preferably 260-500 Pa, and a solution collecting area at the bottom of the devolatilization tank is used for obtaining devolatilized fluid.
The volatile content in the SAN resin obtained after the first devolatilization is 3000 ppm; the content of the volatile component reaches 2000ppm after the first cyclic reflux devolatilization, and reaches 1300ppm after the second cyclic reflux devolatilization, which already meets the requirements.
Example 2
In this embodiment, the silicone fluid is taken as an example, and specifically includes but is not limited to silicone acrylate, polydimethylsiloxane, propyl trimethoxysilane, and the like, and the polymer is generally used as an auxiliary agent and has great demand potential in the market, but because the addition amount is small and the price is high, a small-batch production mode is generally adopted in the processing of a production side, but because the production amount of each batch is small, the flow is insufficient in the devolatilization process, the phenomena of flow breaking, plate drying, and the like are frequently generated, the waste of materials is caused, and the devolatilization efficiency is reduced at the same time.
Taking organic silicon acrylate as an example, the devolatilization process specifically comprises the following steps:
(1) the fluid is conveyed to a preheater 2 through a melt pump 1, and the fluid is mixed and preheated in the preheater 2;
(2) the fluid flows into the devolatilization tank 3 after being preheated, a falling film is formed by the distribution disc 301 and the falling film element in the devolatilization tank 3, the first devolatilization is carried out, and the fluid after the devolatilization flows into the liquid storage area of the devolatilization tank 3;
(3) opening a valve at the bottom of the devolatilization tank, setting a reflux ratio, adjusting an inlet valve of the preheater 2, setting the reflux ratio as required, reducing the flow rate of the fluid to be flowed into the preheater 2, adjusting the valve at the bottom of the devolatilization tank, completely or partially refluxing the devolatilized fluid through a shunt melt pump 12, entering a circulation pipeline 5 through a return pipeline 15 through a connecting end B to be mixed with the fluid which is not devolatilized, further mixing the fluid uniformly through a static mixer 501, entering the preheater 2, supplementing the fluid which is not devolatilized into the preheater 2, enabling the flow rate of the fluid which finally flows into the preheater 2 to be the same as the flow rate of the fluid which flows into the preheater 2 before the adjusting valve, and keeping the fluid which is not refluxed in a liquid storage area of the devolatilization tank 3 or pumping the fluid into a collecting device;
(4) after all the fluids are devolatilized, the devolatilized fluids are pumped into a collecting device through a split-flow melt pump 10.
Preferably, in the step (2) and the step (3), the devolatilization process of the devolatilization tank can be assisted by introducing a stripping agent through a stripping agent input port 303 to assist devolatilization, so as to improve devolatilization efficiency, wherein the stripping agent can be steam or other inert gases.
Specifically, the organic silicon acrylate solution containing 60 wt% of organic silicon acrylate and toluene as a solvent enters a preheater through a polymer solution flow pipeline, is preheated to 160 ℃, is decompressed through an adjusting valve, enters a primary devolatilization tank for devolatilization, and has the temperature of 120-150 ℃, preferably 130-140 ℃, and the operating pressure of 0.6-1 MPa, preferably 0.8-1 MPa. And obtaining the devolatilized fluid in a solution collecting area at the bottom of the devolatilization tank. Preferably, the devolatilized solvent is recovered after being removed through a devolatilization outlet at the top of the devolatilization tank.
The volatile content in the silicone acrylate obtained after devolatilization was 1200 ppm.
Example 3
This example further illustrates the technical solution of the present invention by taking a low-viscosity fluid as an example, and the low-viscosity fluid specifically includes, but is not limited to, polyurethane polymer, carbonate, polysulfone, nylon, polyolefin, polyester, polystyrene, etc.
Chinese patent CN112321754A discloses a polymer solution devolatilization device and method, the device comprises two devolatilization units for devolatilizing polymer solution, a shell-and-tube heat exchanger is arranged between the two devolatilization units, the three units form an integrated structure, and devolatilization can be rapidly realized. However, the apparatus exhibits a fast flow pattern for less viscous polymer solutions, and although the rate of devolatilization is increased, the efficiency is not high.
Referring to fig. 2, this embodiment includes two devolatilization devices connected in series, and each devolatilization device includes a melt pump, a preheater and a devolatilization tank, which are connected once, wherein the three units of the one-level melt pump 6, the one-level preheater 7 and the one-level devolatilization tank 8 of the one-level devolatilization device are sequentially connected through a circulation pipeline. A distribution plate 801 and a falling film element are arranged in the first-stage devolatilization tank 8.
The three units of second grade melt pump 6, second grade pre-heater 7 and second grade devolatilization jar 8 of second grade devolatilization device connect gradually, and wherein, second grade melt pump 9 and second grade pre-heater 10 pass through circulation pipe connection, and second grade pre-heater 10 is fixed on the top of second grade devolatilization jar 11, forms an overall structure. The connection structure of the preheater 2 and the devolatilizer tank 3 in example 1 can be selected as a specific structure.
The bottom of the primary devolatilization tank 8 is connected with the top of the secondary preheater 10 through a flow line 5. Preferably, a static mixer 501 is provided on the flow line 5, which can uniformly mix the fluids to be flowed into the preheater 10 from different lines.
The bottom outlet of the second-stage devolatilization tank 11 is provided with a shunt melt pump 12, the shunt melt pump 12 is respectively connected with a collecting device and a first-stage devolatilization device and/or a second-stage devolatilization device through a circulation pipeline, the connecting end is provided with a valve, and a circulation passage can be arranged according to the specific situation of production. Specifically, the split-flow melt pump 12 is connected with the first-stage devolatilization device and the second-stage devolatilization device through the return pipeline 15, and the return pipeline 15 is provided with a plurality of heat exchangers 1501, so that the situation that the return pipeline is too long and the returned fluid is solidified to block the pipeline is prevented.
The return line 15 is the link A and link B respectively with the one-level device and the second grade device of devolatilizing, wherein, link A locates between one-level melt pump 6 and one-level pre-heater 7, is equipped with one-level flow valve 13 between link A and the one-level melt pump 6. The connecting end B is arranged between the secondary melt pump 9 and the secondary preheater 10, and a secondary flow valve 14 is arranged between the connecting end B and the secondary melt pump 9. That is, the first-stage devolatilization device and/or the second-stage devolatilization device can respectively form a circulating structure, after the first devolatilization, the polymer at the outlet of the shunt melt pump 12 passes through a detector to determine whether the content of volatile components meets the requirements, and directly enters the collecting device after meeting the requirements, and if not, the first-stage flow valve 13 or the second-stage flow valve 14 can be opened again to enter the devolatilization procedure again for secondary devolatilization. Preferably, the first and second electrodes are formed of a metal,
using the above apparatus, devolatilization was carried out using a polyurethane solution as an example. The polyurethane is a prepolymer formed by the reaction of aliphatic and aromatic monomers containing diisocyanate groups and polyester or polyether containing dihydric or polyhydric alcohols, low-molecular binary, ternary or quaternary polyester or polyether can enable a polyurethane reaction system to rapidly carry out chain extension and crosslinking, and meanwhile, a large amount of small-molecular compounds are generally introduced into the production of polyurethane products, especially small molecules are introduced into a foaming material to form a network interpenetrating structure with polyurethane molecules to improve the performance of the foaming material, so a large amount of unreacted monomers and small molecules remain in the polyurethane material, and the devolatilization process is particularly important.
The polyurethane solution devolatilization process specifically comprises the following steps:
(1) the fluid is conveyed to a primary preheater 7 through a primary melt pump 6, and the fluid is mixed and preheated in the primary preheater 7;
(2) the fluid flows into the first-stage devolatilization tank 8 after being preheated, and forms a falling film through a distribution disc 801 and a falling film element in the first-stage devolatilization tank 8 to carry out first devolatilization;
(3) the fluid after the first devolatilization is input into a secondary preheater 10 through a secondary melt pump 9, the fluid after the rapid mixing and preheating directly enters a secondary devolatilization tank 11 for secondary devolatilization under the action of self gravity, and the devolatilization completed fluid flows into a liquid storage area of the devolatilization tank;
(4) opening a valve at the bottom of the devolatilization tank, and sampling to detect the devolatilization rate of the fluid; the qualified fluid is conveyed to a collecting device through a separation melt pump 12;
(5) the unqualified fluid flows back to the primary preheater 7 or the secondary preheater 10 through the connecting end A or B of the return pipeline 15 and is devolatilized again.
Specifically, a 60 wt% polyurethane high polymer solution and toluene as a solvent enter a secondary preheater through a polymer solution circulation pipeline, are preheated to 200 ℃, enter a primary devolatilization tank for devolatilization after being decompressed by an adjusting valve, have the temperature of 180 ℃ in the tank and the operating pressure of 1MPa, are preheated by the secondary preheater and are devolatilized by a secondary devolatilization tank, obtain a polymer solution with the polyurethane content of 98% in a solution collection area at the bottom of the secondary devolatilization tank, pass through a heater at the bottom of a flash tank, have the working temperature of 190 ℃ in the secondary preheater, have the operating temperature of 165-175 ℃ in the secondary devolatilization tank and the operating pressure of 50-200 Pa, and preferably 85-125 Pa.
The volatile content in the polyurethane obtained after the first devolatilization is 5000 ppm; 3000ppm is achieved after the first cyclic reflux devolatilization, 2600ppm is achieved after the second cyclic reflux devolatilization, and the requirements are already met.
The devolatilization process of the present invention can be implemented by modifying the devolatilization apparatus of the prior art according to the actual situation of the production side without being limited to the devolatilization apparatus described in the above embodiments, by adding a melt pump to the outlet of the devolatilization tank of the prior art, and then re-devolatilizing the devolatilized fluid again by returning the devolatilized fluid to the preheater, and by keeping the apparatus of the prior art. Therefore, small-batch materials can be processed in large-scale equipment, the use efficiency of the equipment is improved, the cost is saved, and the energy consumption is reduced.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A cyclic supplement type devolatilization device is characterized by at least comprising a first-stage devolatilization device, wherein the first-stage devolatilization device comprises a melt pump, a preheater and a devolatilization tank which are sequentially connected in series;
the outlet of the devolatilization tank is provided with a shunt melt pump, and the shunt melt pump is connected with the inlet of the preheater to ensure that the preheater and the devolatilization tank form a circulation passage.
2. The cyclic supplemental devolatilizer as claimed in claim 1 wherein said preheater and said devolatilizer are of unitary construction without tubular connections, the bottom portion of said preheater being affixed to the top portion of said devolatilizer and extending axially through said devolatilizer into the tank, the fluid flowing directly into said devolatilizer through said preheater.
3. The cyclic supplemental devolatilization apparatus as claimed in claim 1 or claim 2, wherein said preheater is a single pass tubular heat exchanger, with static mixing elements radially disposed within the tubes; the inner wall of the tube array is provided with a convex pattern structure so as to increase the surface area of the inner wall of the tube array and improve the contact area and the retention time of the tube pass of the fluid.
4. The cyclic supplemental devolatilizer as claimed in claim 1 or claim 2 wherein said devolatilizer tank is provided at a bottom portion thereof with an inlet for a stripping agent.
5. The recycling supplemental devolatilization apparatus as claimed in claim 1 or 2, wherein a falling film evaporator is provided in said devolatilization tank, said falling film evaporator comprises a distribution plate and a falling film element, said distribution plate has a plurality of film distribution holes arranged therein, the fluid flows through said preheater to said distribution plate, and after being uniformly distributed through said film distribution holes, said fluid passes through said falling film element to form a uniform falling film.
6. The cyclic supplemental devolatilizer as claimed in claim 1 or claim 2 wherein said devolatilizer can be used in multiple stages, and the outlet of said devolatilizer tank is connected to the inlet of the preheater of any stage to form a circulation path.
7. The cyclic supplemental devolatilizer of claim 1 wherein said split-flow melt pump is connected to said preheater by a return line, said return line having at least one heat exchanger disposed therein.
8. The cyclic supplemental devolatilizer of claim 1 wherein said melt pump is connected to said preheater by a flow line, said flow line having a static mixer disposed therein to provide uniform mixing of the fluids in the different lines.
9. A cyclic supplemental devolatilization process using the devolatilizer of any of claims 1 to 8 comprising the steps of:
(1) the melt pump delivers fluid to the preheater;
(2) the fluid flows onto the distribution disc through the preheater and forms a falling film through the film distribution holes on the distribution disc;
(3) the fluid flows to a liquid storage area of the devolatilization tank under the action of self gravity;
(4) setting a reflux ratio, adjusting an inlet valve of the preheater, adjusting the flow of the valve according to the reflux ratio, simultaneously adjusting a valve at the bottom of the devolatilization tank, refluxing the devolatilized fluid into the preheater through a shunt melt pump, and refluxing all or part of the fluid to the inlet of the preheater to supplement the flow of the fluid in the preheater;
(5) and (4) the fluid detected to be qualified flows into a collecting device.
10. The cyclic supplemental devolatilization process as claimed in claim 9 wherein in step (5), the fluid can be returned to the preheater again when it is not tested properly, and devolatilized again, and can be recycled for a plurality of times until it is tested properly and finally collected.
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| CN202111147347.5A CN113769423A (en) | 2021-09-29 | 2021-09-29 | Cyclic supplement type devolatilization device and process |
| PCT/CN2022/105888 WO2023050978A1 (en) | 2021-09-29 | 2022-07-15 | Cyclic supplementary devolatilization apparatus and process |
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| WO2023050978A1 (en) * | 2021-09-29 | 2023-04-06 | 华东理工大学 | Cyclic supplementary devolatilization apparatus and process |
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| EP4445979A1 (en) * | 2023-04-11 | 2024-10-16 | Sulzer Management AG | A multi-stage devolatilization apparatus comprising at least one static mixer |
| CN117960101B (en) * | 2024-03-28 | 2024-06-07 | 天津君宇科技股份有限公司 | High-conversion-rate reaction concentration devolatilization system for producing high-viscosity polymer elastomer |
| CN118059789B (en) * | 2024-04-19 | 2024-07-02 | 天津君宇科技股份有限公司 | Process equipment and process for continuously preparing POE |
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