CN212610377U - Continuous solution polymerization device based on LCST - Google Patents
Continuous solution polymerization device based on LCST Download PDFInfo
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- CN212610377U CN212610377U CN202020991815.1U CN202020991815U CN212610377U CN 212610377 U CN212610377 U CN 212610377U CN 202020991815 U CN202020991815 U CN 202020991815U CN 212610377 U CN212610377 U CN 212610377U
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Abstract
The utility model discloses a continuous solution polymerization device based on LCST, including: a raw material storage tank (1) for storing reaction raw materials; a supercritical fluid storage tank (2) for storing a supercritical fluid; a first material inlet of the reactor (3) is communicated with a material outlet of the raw material storage tank (1) and is used for carrying out polymerization reaction on reaction raw materials to generate a polymer solution containing a solvent, a polymer and a monomer; and a liquid-liquid separation tank (4), wherein a first material inlet of the liquid-liquid separation tank is communicated with a material outlet of the reactor (3), and a second material inlet of the liquid-liquid separation tank is communicated with a material outlet of the supercritical fluid storage tank (2) and is used for separating the polymer solution into a dense phase rich in polymer and a dilute phase rich in solvent. Compared with the prior art, the utility model discloses a continuous solution polymerization device can carry out liquid-liquid separation to polymer solution at the lower temperature.
Description
Technical Field
The utility model relates to a solution polymerization technical field specifically indicates a continuous solution polymerization device based on LCST.
Background
Solution polymerization is an important synthetic method in the polymer synthesis process, the generated polymer can be dissolved in a solvent, the product is a solution, also called homogeneous solution polymerization, the reaction is generally carried out under the pressure of 2.0-4.0 MPa, the temperature is about 90-200 ℃, after the reaction is finished, the separation technology (also called devolatilization unit) of the polymer and the solution often determines the energy consumption of the whole process, in the general knowledge, the energy consumption of mechanical separation is often far less than that of heat separation, but the mechanical separation requires a system to naturally phase separate, but the system is often homogeneous, so people can generally think of the scheme that the polymer solution is heated and evaporated to separate the solution polymer, and certainly, the process also has many difficulties, such as reducing the pressure to low pressure (about 0.1-0.5 MPa), providing enough heat and other problems, however, the energy consumption is quite large when all polymer solutions are evaporated, and in addition, a large amount of evaporation gas is required to return to units such as a solvent recovery unit for recovery, so that the energy consumption of a subsequent rectification recovery unit is also quite large.
Therefore, people also continuously explore and research the separation technology of the polymer and the solution, and some processes adopt a liquid-liquid separation method to separate the polymer solution. The polymer Solution can exhibit a Low Critical Solution Temperature (LCST) phenomenon, also known as the minimum Solution Temperature. The homogeneous polymer solution, as the temperature rises, disappears after reaching a certain temperature point, to form two liquid phases, namely a lean phase and a dense phase, wherein the dense phase contains most of the polymer and the lean phase contains a trace amount of the polymer. Since the phase separation temperature is usually much higher than the reaction temperature, it is necessary to heat the reaction product and then perform phase separation using the LCST principle to separate the polymer liquid from the reaction product. For example, patent application No. CN201680032503.4 (publication No. CN107614541A), entitled "continuous solution polymerization process", discloses a process for continuous solution polymerization, which may include polymerizing one or more monomers and comonomers in the presence of a solvent in a polymerization reactor to produce a polymer solution; determining the composition of the polymer solution exiting the polymerization reactor in an online manner; determining at least one of a critical pressure or a critical temperature; comparing the critical pressure and/or critical temperature to the actual temperature of the polymer solution and the actual pressure of the polymer solution; heating or cooling the polymer solution to a temperature within 50 ℃ of the critical temperature; and passing the polymer solution through a pressure letdown valve into a liquid-liquid separator, wherein the pressure of the polymer solution is reduced or increased to a pressure within 50psig of the critical pressure to initiate separation of the polymer solution into two liquid phases.
In addition, in the industry, normal hexane is generally used as a solvent in the liquid phase polymerization reaction, the critical temperature of the normal hexane is 234 ℃, the critical temperature of comonomer 1-octene is 294 ℃, the optimal reaction temperature is generally about 130 ℃, and the critical temperature of the system is far higher than the reaction temperature, the patent also mentions that the heating is needed to reach the critical temperature within 50 ℃, and the method needs to maintain the temperature in a higher range, and the reaction activity of a polymerization reaction catalyst is increased sharply along with the temperature increase, so that the reaction still occurs in the liquid-liquid separation tank, and the possibility of polymerization and even implosion exists in the liquid-liquid separation tank.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve the technical problem that to prior art's current situation, provide one kind and can carry out the continuous solution polymerization device based on LCST of liquid-liquid separation to polymer solution under being equal to or being less than the polymerization temperature slightly, this continuous solution polymerization device need not to set up extra rising temperature device and heaies up polymer solution.
The utility model provides a technical scheme that above-mentioned technical problem adopted does: a continuous solution polymerization device based on LCST, characterized by comprising:
the raw material storage tank is used for storing reaction raw materials;
a supercritical fluid storage tank for storing a supercritical fluid;
a first material inlet of the reactor is communicated with a material outlet of the raw material storage tank and is used for carrying out polymerization reaction on reaction raw materials to generate a polymer solution containing a solvent, a polymer and a monomer; and
and the liquid-liquid separation tank is provided with a first material inlet communicated with the material outlet of the reactor, and a second material inlet communicated with the material outlet of the supercritical fluid storage tank, and is used for separating the polymer solution into a polymer-rich dense phase and a solvent-rich dilute phase.
For recovering the dilute phase rich in solvent, the method also comprises
And the inlet of the first booster pump is communicated with the top outlet of the liquid-liquid separation tank, and the outlet of the first booster pump is communicated with the second material inlet of the reactor, so that the dilute phase rich in the solvent is recycled into the reactor.
For further processing of the dense phase rich in polymer, it also comprises
And the material inlet of the post-treatment system is communicated with the bottom outlet of the liquid-liquid separation tank and is used for carrying out post-treatment on the dense phase rich in the polymer to obtain the polymer.
In order to achieve solvent and unreacted monomer and comonomer recovery and polymer extrusion in the dense phase rich in polymer, the post-processing system comprises a solvent recovery unit for recovering solvent into the reactor and an extrusion drying unit for extruding polymer.
Preferably, the solvent recovery unit comprises
The material inlet of the flash evaporation equipment is communicated with the bottom outlet of the liquid-liquid separation tank and is used for carrying out flash evaporation on the dense phase rich in the polymer;
a first gas-liquid separation tank having a feed inlet communicating with the feed outlet of the flash apparatus for separating a dense phase rich in polymer into a gas phase comprising monomer, a major amount of solvent and a liquid phase comprising polymer and a minor amount of solvent;
a first material inlet of the first rectifying tower is communicated with a gas-phase outlet at the top of the first gas-liquid separation tank and is used for recovering most of the solvent and part of unreacted monomers and comonomers;
a first material inlet of the solvent storage tank is communicated with a top liquid phase outlet of the first rectifying tower; and
the inlet of the second booster pump is communicated with the material outlet of the solvent storage tank, and the outlet of the second booster pump is communicated with the third material inlet of the reactor;
and a material inlet of the extrusion drying unit is communicated with a bottom liquid phase outlet of the first gas-liquid separation tank.
Furthermore, the solvent recovery unit also comprises
A material inlet of the second rectifying tower is communicated with a bottom outlet of the first rectifying tower and is used for refining partial solvent and removing oligomers and heavy substances, the refined solvent is arranged at the top of the tower, a catalyst, a cocatalyst, a stabilizer and the like are removed, the catalyst and the like are added in the polymerization reaction by conventional means, so that the preparation section of the catalyst and the like is not shown, and the oligomers and the heavy substances are arranged at the bottom of the tower;
and the top outlet of the second rectifying tower is communicated with the second material inlet of the solvent storage tank.
Preferably, the extrusion drying unit comprises
And the extruder is provided with a water replenishing port, a solvent outlet and an extrusion port, a material inlet of the extruder is communicated with a liquid phase outlet at the bottom of the first gas-liquid separation tank, a solvent outlet of the extruder is communicated with a second material inlet of the first rectifying tower, and the extruder is used for pumping out the solvent of the polymer solution and extruding a polymer product, providing heat in the extruder and carrying out drying vaporization to remove a small amount of hexane or other heavy substances, such as 1-octene and the like.
Preferably, a pressurizing device, such as a fan, a pump and the like, is arranged between the supercritical fluid storage tank and the liquid-liquid separation tank, so as to avoid insufficient power.
Preferably, a heat exchange device is arranged between the supercritical fluid storage tank and the liquid-liquid separation tank, and the supercritical fluid can be heated or cooled before entering the liquid-liquid separation tank.
Preferably, the device further comprises a pipeline mixer, wherein a first material inlet of the pipeline mixer is communicated with a material outlet of the reactor, a second material inlet of the pipeline mixer is communicated with a material outlet of the supercritical fluid storage tank, and a material outlet of the pipeline mixer is communicated with a material inlet of the liquid-liquid separation tank. In this case, the first material inlet and the second material inlet of the liquid-liquid separation tank share one material inlet, and the supercritical fluid is introduced into the pipeline mixer and then enters the liquid-liquid separation tank after being uniformly mixed with the polymer solution, so that the separation of the polymer solution is facilitated.
Preferably, the liquid-liquid separation tank is used for liquid-liquid phase separation, and the liquid-liquid phase separation can be performed by adopting a gravity principle, such as a decanter, and other high-efficiency separation means, such as a liquid-liquid cyclone adopting centrifugal force, an external electric field and other means for accelerating liquid-liquid separation.
Preferably, one or more coolers may be added to remove the heat of reaction before the dilute phase is pumped back to the reactor.
Preferably, the dilute phase may be further treated to stabilize the reaction conditions before entering the reactor, the further treatment comprising adding a polishing bed for removing oligomers, catalysts, etc., and a knock-out pot for removing non-condensable gases.
Preferably, before all the reaction raw materials enter the reactor, at least one separation tank may be provided, after gas-liquid separation in the separation tank, the gas phase may enter the reactor after being pressurized by a compressor, and the liquid phase may enter the reactor after being pressurized by a pump, in which case the gas phase of the reactor may be introduced into the separation tank, and before entering the separation tank, the gas phase may pass through at least one heat exchanger so as to enable even removal of the reaction heat.
The extrusion drying unit may be supplemented with a heating step, evaporated solvent, etc. to a subsequent unit such as a solvent recovery unit in order to remove the volatile components from the polymer to a satisfactory level.
The extrusion drying unit may be operated under vacuum conditions in order to remove the volatile components of the polymer as desired.
The utility model also provides an adopt above-mentioned continuous solution polymerization device's continuous solution polymerization method, its characterized in that includes following step:
(1) reacting the reaction raw materials in a reactor to generate a polymer solution containing a solvent, a polymer, unreacted monomers and comonomers;
(2) discharging the polymer solution into a liquid-liquid separation tank, and simultaneously introducing a supercritical fluid into the liquid-liquid separation tank so as to separate the polymer solution into a polymer-rich dense phase and a solvent-rich dilute phase at a temperature not higher than the polymerization reaction temperature;
the reaction temperature of the reaction raw material in the step (1) is taken as T1, the temperature at which the polymer solution is phase-separated in the step (2) is taken as T2, and the relationship between T2 and T1 satisfies: t2 is less than or equal to T1. Since the environment will dissipate some heat without adding heat, T2 is necessarily no greater than T1.
Preferably, taking the critical temperature of the supercritical fluid in step (2) as T3, the relationship between T3 and T1 satisfies: t3 < T1.
Further, the value of T1 is 90-200 ℃. For example, when the reaction temperature is 100 ℃, a substance having a critical temperature of less than 100 ℃, such as ethylene, propylene, etc., or a mixture thereof may be selected as the supercritical fluid, and when the reaction temperature is 150 ℃, 1-butene, propylene, ethylene, or a mixture thereof may be selected as the supercritical fluid.
Preferably, the supercritical fluid is one or more of nitrogen, methane, ethylene, ethane, propylene, propane, and 1-butene.
Preferably, the supercritical fluid is a supercritical fluid present in the reaction feedstock. When the polymer is a vinyl-based copolymer, ethylene is preferably used as the supercritical fluid; when the polymer is a propylene-based copolymer, propylene is preferably used as the supercritical fluid. In this way, the supercritical fluid can be recovered directly together with the monomer.
Of course, when the supercritical fluid is a non-reaction raw material gas, a supercritical fluid recovery unit may be added to separately recover the supercritical fluid.
Preferably, the supercritical fluid is added in an amount such that the relationship between T2 and T1 satisfies: t2 is less than or equal to (T1-15 ℃).
Compared with the prior art, the utility model has the advantages of: generally speaking, phase separation temperature is far higher than reaction temperature usually, consequently will make polymer liquid-liquid separation, need heat polymer solution earlier, then utilize the LCST principle to carry out the phase separation, and the utility model discloses in, the polymer solution that will produce the reactor gets into liquid-liquid knockout drum, lets in liquid-liquid knockout drum with supercritical fluid simultaneously to reduce polymer solution's LCST, need not to heat polymer solution before getting into liquid-liquid knockout drum, can make polymer solution separate into the dense phase that is rich in polymer and the dilute phase that is rich in the solvent, the energy consumption is lower, and can avoid unreacted material to continue to react in liquid-liquid knockout drum, influences polymer product quality, the safety problem appears even.
Drawings
FIG. 1 is a schematic view showing the structure of example 1 of the continuous solution polymerization apparatus of the present invention;
FIG. 2 is a schematic view showing the structure of comparative example 1 of the continuous solution polymerization apparatus of the present invention;
FIG. 3 is a schematic structural view of example 2 of the continuous solution polymerization apparatus of the present invention;
FIG. 4 is a schematic structural view of comparative example 2 of the continuous solution polymerization apparatus of the present invention;
FIG. 5 is a schematic structural view of example 3 of the continuous solution polymerization apparatus of the present invention;
FIG. 6 is a graph showing the phase separation temperature and the dense phase flow rate of the ethylene-octene copolymer and the n-hexane solution in examples 1 to 3 of the continuous solution polymerization process of the present invention;
FIG. 7 is a graph showing the relationship between the minimum phase separation temperature and the amount of ethylene added for the ethylene-octene copolymer and the n-hexane solution in example 2 of the continuous solution polymerization process of the present invention;
FIG. 8 is a graph showing the relationship between the minimum phase separation temperature of the ethylene-octene copolymer and the n-hexane solution and the amount of propylene added in example 4 of the continuous solution polymerization process of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments.
Example 1:
as shown in FIG. 1, a first preferred embodiment of the LCST-based continuous solution polymerization apparatus of the present invention is shown. The continuous solution polymerization device is characterized by comprising a raw material storage tank 1, a supercritical fluid storage tank 2, a reactor 3, a liquid-liquid separation tank 4, a first booster pump 5 and a subsequent treatment system.
Wherein, the raw material storage tank 1 is used for storing reaction raw materials.
The supercritical fluid storage tank 2 is used for storing the supercritical fluid.
The first material inlet of the reactor 3 is communicated with the material outlet of the raw material storage tank 1 and is used for carrying out polymerization reaction on the reaction raw materials to generate a polymer solution containing a solvent, a polymer and a monomer.
The first material inlet of the liquid-liquid separation tank 4 is communicated with the material outlet of the reactor 3, and the second material inlet is communicated with the material outlet of the supercritical fluid storage tank 2, and is used for separating the polymer solution into a polymer-rich dense phase and a solvent-rich dilute phase.
The inlet of the first booster pump 5 is communicated with the top outlet of the liquid-liquid separation tank 4, and the outlet is communicated with the second material inlet of the reactor 3, and is used for recycling the dilute phase rich in the solvent into the reactor 3.
The post-treatment system is used for post-treating the dense phase rich in polymer to obtain polymer. Because the polymer content in the dense phase rich in polymer is generally about 40-60%, and a large amount of solvent is also present, it is necessary to further remove and recover the solvent from this portion by a solvent recovery unit, and extrude the polymer product by a drying base unit.
The solvent recovery unit is used for recovering the solvent, a rectifying tower is generally adopted for recovery, a small amount of oligomers are generated in the polymerization process, the oligomers need to be discharged in time in order to prevent the excessive oligomers entering the reactor, the oligomers are usually discharged from the tower bottom, the qualified solvent is arranged at the tower top, the qualified solvent is returned to the reactor for recycling after being pressurized by a booster pump, if water needs to be added in the process as a terminator, water can be separated in the solvent recovery unit, the azeotrope of the water and the normal hexane is firstly evaporated at the tower top due to the lowest azeotrope of the water and the normal hexane, the normal hexane can be further treated after being subjected to decanter water cutting, for example, the normal hexane enters the rectifying tower for rectification again, or enters the refined adsorption tower for adsorbing the water, whether the normal hexane enters the rectifying tower or the adsorption tower, the purpose is to remove the water to obtain the qualified normal hexane, and the normal hexane is, of course, the waste water can be sent into the reactor through the storage tank buffer and then sent into the reactor through the booster pump. Meanwhile, the rectification tower can also play a role in recovering monomers and comonomers, wherein the comonomers refer to polymerized monomers with low content in the copolymer, generally refer to non-ethylene alpha olefins such as 1 butene, 1 hexene, 1 octene and the like, and the monomers refer to polymerized monomers with high content in the copolymer, generally refer to ethylene or propylene.
When an excess of comonomer is added during the reaction, it is necessary to recover the comonomer, which is generally recovered by means of a rectification column, in the case of comonomers having a relative volatility higher than that of the solvent (for example n-hexane) (lower boiling point than that of n-hexane at the recovery pressure), defined herein as light comonomers, generally recovered before the solvent, for example 1 butene is obtained at the top of the column in the separation of 1 butene from the solvent, and in the case of comonomers having a relative volatility lower than that of the solvent (for example n-hexane) (higher boiling point than that of n-hexane at the recovery pressure), defined herein as heavy comonomers, generally recovered after the solvent, for example 1 octene is obtained at the bottom of the column in the separation of 1 octene from the solvent. After separation of the comonomer from the solvent, further processing of the comonomer is required, for example separation of light comonomer from non-condensable gases, mainly by rectification separation, separation of heavy copolymeric components and oligomers, either by rectification or by direct heating in a tank.
When the total conversion rate of the reaction is not high during the reaction, usually less than 95%, the monomer needs to be recovered, usually by using a rectifying tower, the top of which is a non-condensable gas such as nitrogen, methane, ethane and the like, and the bottom of which is a comonomer such as propylene and the like. When the overall conversion of the reaction is high, typically greater than 95%, it is also possible to discharge the comonomer directly as non-condensable gas, directly in the light comonomer recovery unit.
The recovery of the above-mentioned solvent, comonomer, monomer usually adopt the rectification operation, and the rectification of multicomponent, can have different separation sequences, for example can separate noncondensable gas, monomer earlier, separate light comonomer again, separate solvent and oligomer again, also can separate noncondensable gas, monomer and light comonomer monomer from the system earlier, then separate to above-mentioned material and obtain light comonomer monomer etc. again, the precedence order of each separation unit does not influence the utility model effect of this process.
The drying and extruding unit is used for separating polymer and non-polymer components, the polymer is a product, the non-polymer (mainly solvent) enters the solvent recovery unit, an extruder is generally used as a main device of the drying and extruding unit, and drying and extruding can be carried out under a vacuum environment in order to reduce the content of the solvent in the polymer product.
In this embodiment, the post-processing system includes a solvent recovery unit 6 for recovering the solvent into the reactor 3 and an extrusion drying unit 7 for extruding the polymer. Specifically, the solvent recovery unit 6 includes a flash apparatus 61, a first gas-liquid separation tank 62, a first rectifying tower 63, a second rectifying tower 64, a solvent storage tank 65, and a second booster pump 66. The extrusion drying unit 7 includes an extruder 71.
Specifically, a material inlet of the flash apparatus 61 is communicated with a bottom outlet of the liquid-liquid separation tank 4, and is used for carrying out flash evaporation on the dense phase rich in the polymer;
a material inlet of the first gas-liquid separation tank 62 communicates with a material outlet of the flash apparatus 61 for separating the dense phase rich in polymer into a gas phase comprising monomer, a major amount of solvent and a liquid phase comprising polymer and a minor amount of solvent;
the first material inlet of the first rectifying tower 63 is communicated with the top gas phase outlet of the first gas-liquid separation tank 62, and the second material inlet is communicated with the solvent outlet of an extruder 71 which is described below, and is used for recovering most of the solvent and part of unreacted monomers and comonomers.
The material inlet of the second rectifying tower 64 is communicated with the bottom outlet of the first rectifying tower 63 for refining part of the solvent and removing the oligomer and heavy substances, the refined solvent is arranged at the top of the tower, the catalyst, the cocatalyst, the stabilizer and the like are arranged, the catalyst and the like are added in the polymerization reaction by conventional means, so the arrangement section of the catalyst and the like is not shown, and the oligomer and heavy substances are arranged at the bottom of the tower.
The first material inlet of the solvent storage tank 65 is communicated with the top liquid phase outlet of the first rectifying tower 63, and the second material inlet is communicated with the top outlet of the second rectifying tower 64.
The inlet of the second booster pump 66 is communicated with the material outlet of the solvent storage tank 65, and the outlet is communicated with the third material inlet of the reactor 3.
The extruder 71 has a water replenishing port, a solvent outlet and an extrusion port, the material inlet is communicated with the liquid phase outlet at the bottom of the first gas-liquid separation tank 62 and is used for extracting the solvent of the polymer solution and extruding the polymer product, and heat is provided in the extruder to dry and evaporate and remove a small amount of hexane or other heavy substances, such as 1-octene and the like.
Comparative example 1:
as shown in fig. 2, the difference from embodiment 1 is that: in comparative example 1, the supercritical fluid storage tank 2, the liquid-liquid separation tank 4, and the first booster pump 5 were omitted, and the material inlet of the flash evaporation apparatus 61 was directly connected to the material outlet of the reactor 3.
The reaction raw material discharged from the raw material storage tank 1 in the comparative example 1 was denoted as S1-F, the polymer product discharged from the extrusion port of the extruder 71 was denoted as S1-P, and the non-condensable gas produced at the top outlet of the first rectifying tower 63 was denoted as S1-V;
in example 1, the reaction raw material discharged from the raw material storage tank 1 is recorded as S2-F, the supercritical fluid discharged from the supercritical fluid storage tank 2 is recorded as S2-S, the polymer product discharged from the extrusion port of the extruder 71 is recorded as S2-P, and the non-condensable gas produced at the top outlet of the first rectifying tower 63 is recorded as S2-V;
the polymerization reaction is carried out in a reactor by using reaction raw materials of ethylene, 1 octene and n-hexane solvent, the reaction conditions are all 105 ℃, 3.0MPaG, the mixture gas of 1 butene and ethylene is used as a supercritical fluid in example 1, the process parameters of each material flow in comparative example 1 and example 1 are shown in table 1, and the heat exchange amount of a main energy consumption device in comparative example 1 and example 1 is shown in table 2.
Table 1 process parameters for each stream in comparative example 1 and example 1
Table 2 heat exchange amount of main energy consumption device in comparative example 1 and example 1
From the data in tables 1 and 2, it can be seen that:
(1) the feed flow rates of example 1 and comparative example 1 in table 1 were substantially the same, in comparative example 1, 1-butene and ethylene were fed mixed together and were S1-F, the feed of example 1 was ethylene feed S2-F and S2-S fed as a supercritical fluid, and the reaction conditions were the same, since the total amount of solvent and the like to be subsequently recovered in example 1 was much smaller than that in comparative example (most of which was returned from the dilute phase), it was seen that the exhaust gas emission of example 1 was also much smaller than that in comparative example 1;
(2) the main energy consumption of the example 1 and the comparative example 1 are concentrated in the second rectifying tower (the first rectifying tower is not large because of gas phase feeding, and is not compared), and the energy consumption of the flash evaporation equipment and the second rectifying tower is much smaller than that of the comparative example 1 because the polymer is effectively concentrated by the liquid-liquid phase separation process of the example 1, and as can be seen from the table 2, the energy saving of the device of the example 1 is improved by more than 50%.
Example 2:
FIG. 3 shows a second preferred embodiment of the LCST-based continuous solution polymerization apparatus of the present invention. The difference from example 1 is that: in this embodiment, the comonomer is 1-octene, and a first heat exchanger 81 is additionally provided between the liquid-liquid separation tank 4 and the first booster pump 5 for removing the reaction heat.
Comparative example 2:
as shown in fig. 4, the difference from embodiment 2 is that: in this comparative example 2, the supercritical fluid storage tank 2 is omitted, and the second heat exchanger 82 and the third heat exchanger 83 are additionally arranged between the reactor 3 and the liquid-liquid separation tank 4, the third heat exchanger 83 is used for heating the material at the outlet of the reactor to the critical temperature of less than 50 ℃, the second heat exchanger 82 is used for recovering heat to preheat the material flow at the outlet of the reactor, the top outlet of the liquid-liquid separation tank 4 is communicated with the shell pass inlet of the second heat exchanger 82, and the shell pass inlet of the first heat exchanger 81 is communicated with the shell pass outlet of the second heat exchanger 82.
The reaction raw material discharged from the raw material storage tank 1 in the comparative example 2 is marked as S3-F, and the polymer-rich dense phase discharged from the outlet at the bottom of the liquid-liquid separation tank 4 is marked as S3-P;
the reaction raw material discharged from a raw material storage tank 1 in example 2 is recorded as S4-F, the supercritical fluid discharged from a supercritical fluid storage tank 2 is recorded as S4-S, and the dense phase rich in polymer discharged from an outlet at the bottom of a liquid-liquid separation tank 4 is recorded as S4-P;
the reaction raw materials of ethylene, 1 octene and n-hexane solvent are polymerized in a reactor under the reaction conditions of 135 ℃ and 3.8MPaG, and in example 2, the ethylene is used as a supercritical fluid, and most of the ethylene returns to the reactor along with a dilute phase, so that the feeding amount of the ethylene in the raw material can be reduced. The process parameters of each stream in comparative example 2 and example 2 are shown in table 3, and the heat exchange amount of the main energy consumption device in comparative example 2 and example 2 is shown in table 4.
Table 3 process parameters for each stream in comparative example 2 and example 2
Note: in comparative example 2, the temperature of the stream between the reactor 3 and the second heat exchanger 82 was 135 ℃, the temperature of the stream between the second heat exchanger 82 and the third heat exchanger 83 was 153.29 ℃, the temperature of the stream between the third heat exchanger 83 and the liquid-liquid separation tank 4 was 184 ℃, the temperature of the stream between the liquid-liquid separation tank 4 and the second heat exchanger 82 was 184 ℃, the temperature of the stream between the second heat exchanger 82 and the first heat exchanger 81 was 145 ℃, the temperature of the stream between the first heat exchanger 81 and the first booster pump 5 was 40 ℃, and the temperature of the stream between the first booster pump 5 and the reactor 3 was 40.96 ℃;
in example 2, the temperature of the stream between the reactor 3 and the liquid-liquid separation tank 4 was 135 ℃, the temperature of the stream between the liquid-liquid separation tank 4 and the first heat exchanger 81 was 135 ℃, the temperature of the stream between the first heat exchanger 81 and the first booster pump 5 was 40 ℃, and the temperature of the stream between the first booster pump 5 and the reactor 3 was 41.02 ℃.
Table 4 heat exchange amount of main energy consumption device in comparative example 2 and example 2
From the data in tables 3 and 4, it can be seen that:
(1) as can be seen from Table 3, in comparative example 2, if the liquid-liquid separation is to be effectively carried out, the temperature needs to be raised to about 184 ℃, so that not only are a lot of heat exchange equipment added, the energy consumption and the operability increased, but also unreacted monomers may continue to react at 184 ℃, the product quality is affected if the temperature is light, and safety accidents occur if the temperature is heavy;
(2) it can be seen from table 4 that the boost power of first booster pump is very little, and can be neglected almost, and be used for moving the first heat exchanger of heat, the heat transfer volume ratio of embodiment 2 is slightly bigger than that of comparison 2, moves heat capacity more excellent a little, adopts the utility model discloses after the technology, embodiment 2 has saved the heating step, has consequently directly saved 1518.81kW, and energy-conserving benefit is very obvious.
Example 3:
FIG. 5 shows a third preferred embodiment of the LCST-based continuous solution polymerization apparatus of the present invention. The difference from example 1 is that:
in this embodiment, at least one second gas-liquid separation tank 9 is disposed between the raw material storage tank 1 and the reactor 3, a gas phase outlet of the second gas-liquid separation tank 9 is connected to the reactor 3 through a compressor 91, a liquid phase outlet of the second gas-liquid separation tank 9 is connected to the reactor 3 through a third booster pump 92, a gas phase outlet of the reactor 3 is connected to the second gas-liquid separation tank 9 through a fourth heat exchanger 93, and the fourth heat exchanger 93 is used for removing reaction heat.
Further, a catalyst disposition unit 10 is additionally provided between the top outlet of the second rectifying column 64 and the reactor 3.
The utility model also provides an adopt the continuous solution polymerization method of the continuous solution polymerization device of above-mentioned embodiment 1, including the following steps:
(1) the reaction raw materials in the raw material storage tank 1 enter a reactor 3 to react to generate a polymer solution containing a solvent, a polymer, unreacted monomers and comonomers;
(2) discharging the polymer solution in the reactor 3 into a liquid-liquid separation tank 4, and simultaneously introducing the supercritical fluid in the supercritical fluid storage tank 2 into the liquid-liquid separation tank 4 so as to separate the polymer solution into a dense phase rich in the polymer and a dilute phase rich in the solvent;
(3) the dilute phase rich in the solvent is discharged from the top outlet of the liquid-liquid separation tank 4, pressurized by a booster pump 5 and then returned to the reactor 3;
(4) the dense phase rich in the polymer is discharged from the outlet at the bottom of the liquid-liquid separation tank 4 and then is treated by a subsequent treatment system to obtain a polymer product, specifically:
the dense phase rich in the polymer is discharged from the bottom outlet of the liquid-liquid separation tank 4 and enters a flash evaporation device 61 for heating and flash evaporation;
secondly, the flash-evaporated dense phase enters a first gas-liquid separation tank 62 to be separated into a gas phase containing the monomer and a large amount of solvent and a liquid phase containing the polymer and a small amount of solvent;
thirdly, gas phase containing the monomers and a large amount of solvent is discharged from a gas phase outlet at the top of the first gas-liquid separation tank 62 and then sequentially enters a first rectifying tower 63 and a second rectifying tower 64;
discharging a large amount of solvent from top liquid phase outlets of the first rectifying tower 63 and the second rectifying tower 64, then entering a solvent storage tank 65, boosting the solvent by a second booster pump 66, and then returning the solvent to the reactor 3, and discharging the oligomer from a bottom outlet of the second rectifying tower 64;
discharging the liquid phase containing the polymer and a small amount of solvent from a liquid phase outlet at the bottom of the liquid separation tank 62, feeding the liquid phase into an extruder 71, pumping out the residual solvent by the extruder 71, feeding the residual solvent into the first rectifying tower 63 through a solvent outlet, and extruding the polymer through an extrusion opening to obtain a polymer product.
Comparative example 1:
referring to the above continuous solution polymerization method, ethylene, 1-octene and n-hexane solvent as reaction raw materials were subjected to polymerization reaction in a reactor to obtain an ethylene-octene copolymer (copolymerization ratio 7:3 (mass ratio)) and an n-hexane solution (containing a small amount of unreacted monomer ethylene and comonomer), the stream having a solid content of 20 wt%, the polymer flow rate of 128.6kg/h, without addition of a supercritical fluid.
Example 1:
the difference from comparative example 1 is that: ethane is added as a supercritical fluid.
Example 2:
the difference from comparative example 1 is that: ethylene is added as a supercritical fluid.
Example 3:
referring to the above continuous solution polymerization method, ethylene, 1-octene and n-hexane solvent as reaction raw materials were subjected to polymerization reaction in a reactor to obtain an ethylene-octene copolymer (copolymerization ratio 8:2 (mass ratio)) and an n-hexane solution (containing a small amount of unreacted monomer ethylene and comonomer) having a solid content of 28.7 wt% and a polymer flow rate of 40kg/h, propylene was added as a supercritical fluid, and propane was added as a supercritical fluid.
FIG. 6 is a graph showing the phase separation temperature of the ethylene-octene copolymer and n-hexane solution in comparative example 1, example 1 and example 2 and the dense phase flow;
FIG. 7 is a graph showing the relationship between the minimum phase separation temperature and the amount of ethylene added in the ethylene-octene copolymer and n-hexane solution in example 2;
the relationship between the minimum phase separation temperature of the ethylene-octene copolymer and n-hexane solution in example 4 and the amount of propylene added is shown in FIG. 8.
As can be seen from FIGS. 6-8:
(1) as can be seen from FIG. 6, Ta, Tb and Tc are the lowest liquid-liquid phase separation temperatures under the three conditions, generally, the actual liquid-liquid phase separation temperature in an industrial device is 10-20 ℃ higher than the theoretical temperature, and it can be seen from the graph that the minimum phase separation temperature of the system is about 180 ℃ when no supercritical fluid is added, and the minimum phase separation temperature is respectively reduced to Tb (about 125 ℃) and Tc (about 115 ℃) when ethane or ethylene is added, and thus the LCST is greatly influenced by the addition of the supercritical fluid. It can also be seen from the figure that when the dense phase flow rate is required to be 320kg/h, the reactor discharge must be heated to about 190 ℃ without the addition of a supercritical fluid, whereas for ethylene or ethane the temperatures are about 134 ℃ and 142 ℃, respectively, and are substantially the same as the reaction temperature. Therefore, the reaction temperature can be completely matched by adjusting the addition amount of the supercritical fluid without additionally increasing a heat exchanger for heating;
(2) as can be seen from FIGS. 7 and 8, the more ethylene or propylene is added, the lower the minimum phase separation temperature is, for the ethylene-octene copolymer and n-hexane solution, and it can be seen that the LCST of the polymer solution is inversely related to the addition of the supercritical fluid.
The reaction temperature of the reaction materials was denoted as T1, the temperature at which the polymer solution phase separated was denoted as T2, and the critical temperature of the supercritical fluid was denoted as T3.
Generally, the phase separation temperature is usually much higher than the reaction temperature, so to separate the polymer liquid from the polymer liquid, the polymer solution needs to be heated first, and then the polymer liquid is phase separated by using the principle of LCST. In addition, since the supercritical fluid is generally at normal temperature, the temperature of the liquid-liquid separation tank after mixing is slightly lower than the reaction temperature, that is, the relationship between T2 and T1 satisfies: t2 is less than or equal to T1. Thus, by adding the supercritical fluid in a continuous solution polymerization process, the polymer solution obtained in the solution polymerization tank can be obtained at a level equal to or slightly lower than that of the solution polymerization tank without heating the polymer solution before entering the liquid-liquid separation tank.
The supercritical fluid is a fluid with the critical temperature less than the reaction temperature, namely the relation between T3 and T1 satisfies: t3 < T1. For example, when T1 is 110 ℃, nitrogen, methane, ethylene, ethane, propylene, propane, etc. may be added as the supercritical fluid to the liquid-liquid separation tank, and the critical temperature of each substance is as shown in table 5 below, so as to avoid adding additional substances, and a monomer or comonomer such as ethylene or propylene may be used as the supercritical fluid.
TABLE 5 Critical temperature of the substances
| Components | N2 | CH4 | C2H4 | C2H6 | C3H6 | C3H8 |
| Critical temperature/. degree.C | -146.95 | -82.586 | 9.19 | 32.17 | 91.7 | 96.7 |
In order to ensure the phase separation effect of the liquid-liquid separation tank, in general, the supercritical fluid should be added in an amount such that the minimum phase separation temperature of the liquid-liquid separation is lower than about 15 ℃, for example, the reaction temperature is 130 ℃, and then after a certain amount of supercritical fluid is added into the liquid-liquid separation tank, the minimum liquid-liquid phase separation temperature in the tank should be about 115 ℃ to ensure the phase separation effect, that is, the supercritical fluid should be added in an amount such that the relationship between T2 and T1 is satisfied: t2 is less than or equal to (T1-15 ℃).
Claims (10)
1. A continuous solution polymerization device based on LCST, characterized by comprising:
a raw material storage tank (1) for storing reaction raw materials;
a supercritical fluid storage tank (2) for storing a supercritical fluid;
the first material inlet of the reactor (3) is communicated with the material outlet of the raw material storage tank (1) and is used for carrying out polymerization reaction on reaction raw materials to generate a polymer solution containing a solvent, a polymer and a monomer; and
and the liquid-liquid separation tank (4) is communicated with a material outlet of the reactor (3) through a first material inlet, and is communicated with a material outlet of the supercritical fluid storage tank (2) through a second material inlet, and is used for separating the polymer solution into a dense phase rich in polymer and a dilute phase rich in solvent.
2. The continuous solution polymerization apparatus according to claim 1, wherein: also comprises
And the inlet of the first booster pump (5) is communicated with the top outlet of the liquid-liquid separation tank (4), and the outlet of the first booster pump is communicated with the second material inlet of the reactor (3) and is used for recovering the dilute phase rich in the solvent into the reactor (3).
3. The continuous solution polymerization apparatus according to claim 1, wherein: also comprises
And the material inlet of the post-treatment system is communicated with the bottom outlet of the liquid-liquid separation tank (4) and is used for carrying out post-treatment on the dense phase rich in the polymer to obtain the polymer.
4. The continuous solution polymerization apparatus according to claim 3, wherein: the post-processing system comprises a solvent recovery unit for recovering the solvent into the reactor (3) and an extrusion drying unit for extruding the polymer.
5. The continuous solution polymerization apparatus according to claim 4, wherein: the solvent recovery unit comprises
Flash distillation equipment (61) with a material inlet connected to the bottom outlet of the liquid-liquid separation tank (4) for flashing a dense phase rich in polymer;
a first gas-liquid separation tank (62) having a feed inlet communicating with the feed outlet of the flash apparatus (61) for separating a dense phase rich in polymer into a gas phase comprising monomer, a major amount of solvent and a liquid phase comprising polymer and a minor amount of solvent;
a first rectifying tower (63) with a first material inlet communicated with the top gas-phase outlet of the first gas-liquid separation tank (62) for recovering most of the solvent and part of the unreacted monomer and comonomer;
a solvent storage tank (65), wherein a first material inlet of the solvent storage tank is communicated with a top liquid phase outlet of the first rectifying tower (63); and
a second booster pump (66), the inlet of which is communicated with the material outlet of the solvent storage tank (65), and the outlet of which is communicated with the third material inlet of the reactor (3);
the material inlet of the extrusion drying unit is communicated with the bottom liquid phase outlet of the first gas-liquid separation tank (62).
6. The continuous solution polymerization apparatus according to claim 5, wherein: the solvent recovery unit also comprises
A second rectifying tower (64), wherein a material inlet of the second rectifying tower is communicated with a bottom outlet of the first rectifying tower (63) and is used for refining part of the solvent and removing oligomers and heavy substances;
the top outlet of the second rectifying tower (64) is communicated with the second material inlet of the solvent storage tank (65).
7. The continuous solution polymerization apparatus according to claim 5, wherein: the extrusion drying unit comprises
And the extruder (71) is provided with a water replenishing port, a solvent outlet and an extrusion port, a material inlet of the extruder is communicated with a bottom liquid phase outlet of the first gas-liquid separation tank (62), a solvent outlet of the extruder is communicated with a second material inlet of the first rectifying tower (63) and is used for extracting the solvent of the polymer solution and extruding a polymer product, and heat is provided in the extruder for drying and vaporization.
8. The continuous solution polymerization apparatus according to any one of claims 1 to 7, wherein: the liquid-liquid separation tank (4) is a decanter adopting a gravity principle to perform phase separation, or a liquid-liquid cyclone adopting centrifugal force to perform phase separation, or equipment adopting an external electric field to perform phase separation.
9. The continuous solution polymerization apparatus according to any one of claims 1 to 7, wherein: at least one second gas-liquid separation tank (9) is arranged between the raw material storage tank (1) and the reactor (3), a gas phase outlet of the second gas-liquid separation tank (9) is connected with the reactor (3) through a compressor (91), and a liquid phase outlet of the second gas-liquid separation tank (9) is connected with the reactor (3) through a third booster pump (92).
10. The continuous solution polymerization apparatus according to claim 9, wherein: and a gas-phase outlet of the reactor (3) is connected with the second gas-liquid separation tank (9) through a fourth heat exchanger (93).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111499776A (en) * | 2020-06-03 | 2020-08-07 | 金聚合(宁波)新材料科技有限公司 | Continuous solution polymerization device based on L CST and continuous solution polymerization method adopting continuous solution polymerization device |
| CN115246903A (en) * | 2021-04-28 | 2022-10-28 | 中国石油化工股份有限公司 | Continuous solution polymerization process |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111499776A (en) * | 2020-06-03 | 2020-08-07 | 金聚合(宁波)新材料科技有限公司 | Continuous solution polymerization device based on L CST and continuous solution polymerization method adopting continuous solution polymerization device |
| CN115246903A (en) * | 2021-04-28 | 2022-10-28 | 中国石油化工股份有限公司 | Continuous solution polymerization process |
| CN115246903B (en) * | 2021-04-28 | 2023-09-12 | 中国石油化工股份有限公司 | Continuous solution polymerization process |
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