System and method for devolatilization of polymers

Abstract

The present invention discloses a system and a devolatilization method for devolatilizing polymers, the system comprising: a flash unit for receiving and flashing a polymer solution from a reactor to obtain a first volatile gas phase and a pre-devolatilized polymer solution; a static devolatilization unit, comprising at least two stages of static devolatilizers connected in series, for receiving and heating the pre-devolatilized polymer solution from the flash unit to obtain a second volatile gas phase and a static devolatilized polymer solution; a dynamic devolatilization unit for receiving the static devolatilization polymer solution and heating it in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution; a volatile recovery unit, connected to the static devolatilization unit and the dynamic devolatilization unit, for receiving the second volatile gas phase and the third volatile gas phase. The present invention can obtain an extremely low VOC environmentally friendly polymer product through pre-devolatilization of the flash unit and combined devolatilization of the static devolatilization unit and the dynamic devolatilization unit, and avoids the blockage problem in volatile recovery.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthesis, and in particular to a system and a devolatilization method for polymer devolatilization. Background Art

[0002] Polymer devolatilization is an important process in the chemical industry, especially in the processing of polymer materials and plastics. To obtain high-quality and environmentally friendly materials with very low volatility, this process is very complicated and requires comprehensive consideration of system design, devolatilization equipment, devolatilization method, recovery system, transportation equipment, pipeline and instrument design, equipment layout, etc. according to the characteristics of the polymerization system, such as viscosity, elasticity, solvent boiling point, solvent relative volatility, polymer molecular weight, stability, etc.

[0003] In particular, it is very difficult to obtain low-VOC polymer materials by devolatilization when the polymer in the polymerization system is thermosensitive or thermally unstable, has a low degradation temperature or a high glass transition temperature, and the heavy components in the volatiles have a high boiling point. At present, polymer devolatilization technology at home and abroad is generally developed based on experience and experiments. For different systems, domestic and foreign companies have announced various devolatilization systems, devices and methods.

[0004] CN113207283A discloses a method and process for solution polymerization, wherein the polymer separation process is to increase the polymer solid content from 15-17%wt to 21-27%wt of the polymerization reaction liquid through a special liquid-liquid phase separation process, and then convey the polymer-rich phase to multiple devolatilization containers, wherein each devolatilization container is operated at a lower pressure than the previous devolatilization container to separate the polymer from the volatiles present in the polymer-rich phase.

[0005] CN 112292201A discloses a system for solution polymerization, wherein the separation process comprises a plurality of devolatilization vessels, the plurality of devolatilization vessels being located downstream of the reactor system, wherein each devolatilization vessel is operated at a lower pressure than the previous devolatilization vessel; and a heat exchanger, the heat exchanger being disposed between the two devolatilization vessels and being in fluid communication therewith.

[0006] CN102858415A discloses a devolatilization apparatus and method, which provides an apparatus and method for devolatilizing a flowable material (e.g., a molten polymer and entrained or dissolved solvent or unreacted monomer or comonomer) using a plate heater having a heating channel, the heating channel being designed or operated so that the flowable material is maintained above its bubble point pressure during passage through a larger first zone and then inducing flash in a smaller second zone, or downstream, of the heating channel.

[0007] However, in the industry, most of the systems and methods for devolatilization of polymers emphasize the enhanced removal of a large number of volatiles, such as the optimization of devolatilization equipment and internals in CN102858415A, the enhancement of devolatilization process in CN112292201A, and the selection of inversion or phase separation aids in CN113207283A. The above static devolatilization is only effective for the removal of a large number of volatiles, but polymers often contain 2000 to 5000 ppm of volatiles, which is not only not environmentally friendly, but also often affects the processing and application of polymer materials.

[0008] In addition, a large amount of volatiles in the devolatilizer will carry a small amount of polymer during the process of removal. In practical applications, whether it is condensed by a heat exchanger, separated by a gas-liquid separator, a demister or a cyclone separator for droplet separation, the polymer will be blocked in the pipeline, instrument or equipment, causing the device to shut down. The industry still faces the above problems in the system of polymer devolatilization. Summary of the invention

[0009] In view of this, the main purpose of the present invention is to provide a system and a devolatilization method for polymer devolatilization, through the pre-devolatilization of a flash unit and the combined devolatilization of a static devolatilization unit and a dynamic devolatilization unit, an extremely low VOC environmentally friendly polymer product can be obtained, the VOC content can be less than 300ppm, and the clogging problem in the recovery of volatiles is avoided.

[0010] To achieve the above-mentioned object of the invention, the first aspect of the present invention provides a system for devolatilization of a polymer, comprising:

[0011] a flash unit, located downstream of a reactor for forming a polymer, for receiving and flashing a polymer solution from the reactor to obtain a first volatile gas phase and a pre-devolatilized polymer solution;

[0012] a static devolatilization unit, located downstream of the flash unit, comprising at least two stages of static devolatilizers connected in series, for receiving and heating the pre-devolatilized polymer solution from the flash unit to obtain a second volatile gas phase and a static devolatilized polymer solution;

[0013] A dynamic devolatilization unit, located downstream of the static devolatilization unit, is used to receive the static devolatilization polymer solution from the static devolatilization unit and heat it in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution;

[0014] a volatile component recovery unit, connected to the static devolatilization unit and the dynamic devolatilization unit, and configured to receive the second volatile component gas phase and the third volatile component gas phase;

[0015] The first volatile gas phase includes unreacted light component monomers in the polymer solution; the second volatile gas phase includes the solvent in the polymer solution; and the third volatile gas phase includes the heavy components in the polymer solution.

[0016] In a preferred embodiment, the system further comprises: a preheating unit located between the flash evaporation unit and the static devolatilization unit, for preheating the pre-devolatilization polymer solution from the flash evaporation unit and then feeding it into the static devolatilization unit.

[0017] In a preferred embodiment, in the serially connected static devolatilizers, the pressure inside each static devolatilizer is lower than or equal to the pressure inside the previous static devolatilizer.

[0018] In a preferred embodiment, a first heating device is provided inside the static devolatilizer for heating the pre-devolatilization polymer solution entering the static devolatilization unit.

[0019] In a preferred embodiment, the dynamic devolatilization unit includes a dynamic component for churning the polymer solution and a second heating device for heating the polymer solution.

[0020] In a preferred embodiment, the volatile recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating;

[0021] In a preferred embodiment, the interior of the volatile recovery unit is axially divided into a low-pressure absorption area, a medium-pressure absorption area and a high-pressure absorption area, and at least two second volatile inlets connected to the static devolatilization unit and a third volatile inlet connected to the dynamic devolatilization unit are arranged at different axial positions of the volatile recovery unit.

[0022] Preferably, there are multiple second volatile matter inlets, which are respectively connected to the static devolatilizers.

[0023] In a preferred embodiment, a separation component is provided inside the volatile recovery unit for separating the components in the volatiles to obtain light component monomers, heavy components and solvents respectively.

[0024] In a preferred embodiment, in the flash unit, the first volatile gas phase enters the reactor.

[0025] A second aspect of the present invention provides a method for devolatilizing a polymer, the method comprising:

[0026] The polymer solution formed in the reactor is sent to a flash evaporation unit to flash the polymer solution to obtain a first volatile gas phase and a pre-devolatilized polymer solution;

[0027] The pre-devolatilization polymer solution from the flash unit is sent to a static devolatilization unit, and the pre-devolatilization polymer solution is heated by at least two stages of static devolatilizers connected in series arranged inside the static devolatilization unit to obtain a second volatile gas phase and a static devolatilization polymer solution;

[0028] The static devolatilization polymer solution from the static devolatilization unit is sent to the dynamic devolatilization unit, and the static devolatilization polymer solution is heated in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution;

[0029] The second volatile gas phase in the static devolatilization unit and the third volatile gas phase in the dynamic devolatilization unit are sent to a volatile recovery unit;

[0030] The first volatile gas phase includes unreacted light component monomers in the polymer solution, the second volatile gas phase includes the solvent in the polymer solution, and the third volatile gas phase includes the heavy components in the polymer solution.

[0031] In a preferred embodiment, the method further comprises: preheating the pre-devolatilization polymer solution from the flash unit and then feeding it into the static devolatilization unit, preferably, the preheating temperature is 150-300°C, more preferably 200-260°C.

[0032] In a preferred embodiment, in a multi-stage static devolatilizer connected in series, according to the material flow direction, the operating pressure of the first-stage static devolatilizer is a positive pressure of 0.1 to 6 barG, preferably 2 to 4 barG, and the polymer content at the outlet of the first-stage static devolatilizer is preferably 50% to 80%; the operating pressure of the final static devolatilizer is a negative pressure of 0.1 to 95 kPaA, preferably 0.1 to 5 kPaA, and the polymer content of the final static devolatilizer is preferably 85% to 99.9%.

[0033] In a preferred embodiment, the temperature of the pre-devolatilized polymer solution is heated to 150-300°C, preferably 180-260°C in the static devolatilization unit.

[0034] In a preferred embodiment, the temperature of the statically devolatilized polymer solution heated in the dynamic devolatilization unit is 160-300°C, preferably 180-260°C.

[0035] In a preferred embodiment, the operating pressure in the dynamic devolatilization unit is 0.001 to 1 kPaA, preferably 0.1 to 1 kPaA.

[0036] In a preferred embodiment, the volatile matter recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating, and the heating temperature is 100-300°C, preferably 120-250°C.

[0037] In a preferred embodiment, the interior of the volatile component recovery unit is divided into a low-pressure absorption area, a medium-pressure absorption area and a high-pressure absorption area along the axial direction, so as to perform graded absorption of the volatile components.

[0038] In a preferred embodiment, the method further comprises: separating the components in the volatiles by a separation member disposed inside the volatile recovery unit to obtain light component monomers, heavy components and solvents respectively.

[0039] In a preferred embodiment, the method further comprises: the volatile matter recovery unit controls the pressure of the static devolatilization unit and the dynamic devolatilization unit.

[0040] In a preferred embodiment, the method further comprises: sending the first volatile gas phase in the flash unit into the reactor.

[0041] In a preferred embodiment, the polymer solution is quenched to deactivate the catalyst before being fed into the flash unit.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] According to the system and method of the present invention, the polymer solution formed in the reactor is first sent to a flash evaporation unit, and the flash evaporation polymer solution is used to make the unreacted light component monomers with low boiling point and difficult to liquefy form a first volatile gas phase. In the flash evaporation unit, the first volatile gas phase is removed from the polymer solution to obtain a pre-devolatilized polymer solution; then, the pre-devolatilized polymer solution from the flash evaporation unit is sent to a static devolatilization unit, and the pre-devolatilized polymer solution is heated by at least two stages of static devolatilizers connected in series inside the static devolatilizer to make the solvent therein form a second volatile gas phase. The second volatile gas phase is separated from the pre-devolatilized polymer solution. The static devolatilization polymer solution is separated out, and the mass fraction of the volatile matter can be reduced to less than 5% after the volatile matter is removed in the static devolatilization unit; then, the static devolatilization polymer solution from the static devolatilization unit is sent to the dynamic devolatilization unit, and the static devolatilization polymer solution is heated in a tumbling state so that the heavy components therein form a third volatile gas phase, and the third volatile gas phase is separated from the static devolatilization polymer solution to obtain a dynamic devolatilization polymer solution, and the remaining trace non-volatile components can be almost removed in the dynamic devolatilization unit, so that the volatile matter content in the final polymer reaches 50 to 1000 ppm. The second volatile gas phase in the static devolatilization unit and the third volatile gas phase in the dynamic devolatilization unit can be sent to the volatile recovery unit to further recover the light component monomer, heavy components and solvent.

[0044] In particular, the volatile recovery unit of the present invention can not only realize the function of recovering polymer volatiles, but also couple other functions, including but not limited to: graded absorption of volatiles; separation of absorbed volatiles, separation of light component monomers and solvents and returning them to the reactor, and enrichment of heavy components at the bottom of the tower and discharge from the system; pressure regulation of static devolatilization units and dynamic devolatilization units, etc.

[0045] The connection points of the volatile recovery unit of the present invention with the static devolatilization unit and the dynamic devolatilization unit can be connected at different axial positions according to the pressure requirements of the devolatilization system. The pressure is adjusted by the internal parts of the recovery unit. The recovery unit has built-in anti-clogging internal parts, which can effectively wash the polymers entrained by the volatiles, ensure the efficient and stable operation of the system, and greatly reduce the energy consumption.

[0046] In summary, the present invention can obtain an ultra-low VOC environmentally friendly polymer material through the devolatilization combination of a flash unit, a static devolatilization unit and a dynamic devolatilization unit, and avoids the clogging problem in the recovery of volatiles.

[0047] Other features and advantages of the present invention will be described in detail through the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0049] Figure 1 The present invention is a schematic diagram of a process flow of a system for devolatilization of polymers according to an example.

[0050] Figure 2 The figure is a schematic diagram of another process flow of a system for polymer devolatilization according to an example of the present invention.

[0051] The reference numerals are as follows: reactor 101, flash unit 102, static devolatilization unit 103, dynamic devolatilization unit 104, volatile matter recovery unit 105, compressor 201, heat exchangers 202, 205, 207, first-stage static devolatilizer 203, second-stage static devolatilizer 204, third-stage static devolatilizer 206, reboiler 208, absorption separation tower 209, pressure control tray 210, vacuum pump 211, condenser 212, 213, 214, 215, collecting tank 216, pump 217, pipelines 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319. DETAILED DESCRIPTION

[0052] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0053] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0054] Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] The present invention provides a system for devolatilization of a polymer, comprising:

[0056] a flash unit, located downstream of a reactor for forming a polymer, for receiving and flashing a polymer solution from the reactor to obtain a first volatile gas phase and a pre-devolatilized polymer solution;

[0057] a static devolatilization unit, located downstream of the flash unit, comprising at least two stages of static devolatilizers connected in series, for receiving and heating the pre-devolatilized polymer solution from the flash unit to obtain a second volatile gas phase and a static devolatilized polymer solution;

[0058] A dynamic devolatilization unit, located downstream of the static devolatilization unit, is used to receive the static devolatilization polymer solution from the static devolatilization unit and heat it in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution;

[0059] a volatile component recovery unit, connected to the static devolatilization unit and the dynamic devolatilization unit, and configured to receive the second volatile component gas phase and the third volatile component gas phase;

[0060] Wherein, the first volatile gas phase includes unreacted light component monomers in the polymer solution, such as ethylene; the second volatile gas phase includes the solvent in the polymer solution, such as inert alkanes, such as pentane, methylpentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, hydrogenated naphtha or C5-12 hydrocarbons substituted by a combination thereof; the third volatile gas phase includes heavy components in the polymer solution, such as macromolecular hydrocarbons and / or low molecular weight olefin polymers.

[0061] In the present invention, the flash unit is used to flash the polymer solution so that the unreacted low-boiling, non-liquefiable raw material monomers therein become gas phase (first volatile gas phase) and are separated from the solution. Preferably, the flash is performed under positive pressure of 8 to 12 barG and adiabatic conditions without additional heat input. The operation under this pressure can control the first volatile gas phase of the flash to be mainly low-boiling unreacted monomers, and the solvent content is less than 10%, so as to ensure that the first volatile gas phase returned to the reaction system will not be liquefied when passing through the compressor. In a specific example, a vertical or horizontal flash tank can be used as the flash unit.

[0062] Preferably, the first volatile gas phase obtained in the flash unit of the present invention is sent to the reactor through a pressurizing device without condensation, which effectively simplifies the process and saves energy consumption and equipment investment in the ultra-low temperature cooling zone.

[0063] Preferably, an anti-mist entrainment internal part is arranged inside or outside the flash unit near the outlet of the first volatile gas phase. At the same time, in order to further reduce mist entrainment and ensure the stable operation of the booster equipment connected to the flash unit, the gas velocity of the first volatile gas phase such as the low-boiling point polymerization monomer in the flash unit is ≤12m / s, preferably ≤8m / s, and more preferably ≤6m / s. In a specific embodiment, the gas velocity is controlled by the cross-sectional area of ​​the flash equipment.

[0064] Preferably, the system of the present invention further comprises: a preheating unit located between the flash unit and the static devolatilization unit, which is used to preheat the pre-devolatilization polymer solution from the flash unit and then send it to the static devolatilization unit. In a specific example, a heat exchanger or a heater can be used. Preferably, the preheating temperature is 150-300°C, and more preferably 200-260°C. This temperature range can ensure that the polymer is almost not degraded and can ensure that the solution is in a liquid phase in the heat exchanger and the pipeline.

[0065] In the present invention, the static devolatilization unit is used to heat the pre-devolatilization polymer solution so that the solvent therein becomes a gas phase (second volatile gas phase) and is separated from the solution. The static devolatilization unit is composed of at least n stages (n≥2) of static devolatilizers connected in series, and each stage of static devolatilizers is connected by a process pipeline, a delivery pump and a heat exchange device; preferably, each static devolatilizer has a lower or equal pressure than the previous stage static devolatilizer. Preferably, the operating pressure of the first stage static devolatilizer is a positive pressure of 0.1 to 6 barG, more preferably 2 to 4 barG; and the outlet polymer content is 30% to 80% wt; preferably, the operating pressure of the last stage static devolatilizer is a negative pressure of 0.1 to 95 kPaA, more preferably 0.1 to 5 kPaA, and the outlet polymer content is 85% to 99.9% wt. Among them, the first-stage static devolatilization is used for large-scale devolatilization and is heat transfer control. The pressure is set to 0.1-6 barG. First, it ensures that the volatile matter can be removed in large quantities by lowering the bubble point. Secondly, the pressure is not too low, which leads to excessive gas flow rate and polymer entrainment. The final-stage static devolatilization is a small amount of extreme devolatilization and is mass transfer control. It needs to provide sufficient mass transfer power under high vacuum, so the pressure is preferably 0.1-5 kPaA.

[0066] Preferably, in order to reduce polymer entrainment, the gas velocity of the second volatile gas phase in the polymer solution in each stage of static devolatilizer is ≤20 m / s, preferably ≤15 m / s, and more preferably ≤8 m / s. In a specific embodiment, the gas velocity is controlled by reasonably designing the evaporation capacity of each stage of static devolatilizer and the cross-sectional area of ​​the static devolatilizer.

[0067] Preferably, in order to realize the heating mode of the static devolatilization unit, a first heating device is arranged in the static devolatilizer, preferably at the top of the static devolatilizer, so that the heating temperature of the pre-devolatilized polymer solution therein is 150-300° C., preferably 200-260° C. This temperature range can ensure that the polymer is almost not degraded, and secondly, ensure that the solution is in the liquid phase in the heat exchanger.

[0068] In a specific example, since the pre-devolatilization polymer solution has been heated by a preheating unit before entering the first-stage static devolatilizer, the first-stage static devolatilizer may not be provided with a heating device, while the subsequent stages and even the last stage (2 to n stages) of the static devolatilizer are all provided with a first heating device, such as a heat exchanger or a heater.

[0069] Preferably, the process pipeline from the second volatile gas phase outlet of each static devolatilizer to the volatile recovery unit is not provided with valves and any condensation or gas-liquid separation equipment, and the pipeline design is ensured to have no liquid bag and should be provided with heating to avoid blockage.

[0070] In the present invention, the dynamic devolatilization unit is located downstream of the static devolatilization unit. The concentrated polymer solution (volatile matter is reduced to a mass fraction of less than 5%) after the volatile matter is removed by a multi-stage static devolatilizer is sent to the dynamic devolatilization unit by a high-viscosity delivery pump, such as a gear pump, a screw pump or other delivery device. The trace amount of non-volatile components (heavy components) are heated under near-vacuum conditions to become gas phase and removed from the polymer solution to achieve deep removal. The dynamic devolatilization unit includes a dynamic component for churning the polymer solution and a second heating device for heating the polymer solution. By forcing the surface of the polymer solution to be renewed, the volatile matter encapsulated in the polymer is accelerated to transfer and heat. Preferably, the heat transfer coefficient is 5 to 100 w / m2.℃, more preferably 20 to 80 w / m2.℃;

[0071] Preferably, the polymer content in the feed solution of the dynamic devolatilization unit is 85-99.9%wt, more preferably the polymer content is 95-99%wt; preferably, the volatile content in the polymer separated by the dynamic devolatilization unit is 50-1000ppm, more preferably 50-300ppm; preferably, the operating pressure of the dynamic devolatilization unit is 0.001-1kPaA, more preferably 0.1-1kPaA. The higher the concentration of volatiles in the feed of the dynamic devolatilization unit, the more difficult it is to remove, so it is best not to exceed 5%, and under the forced surface renewal and sufficient heating of the dynamic devolatilization, an extremely high vacuum degree is required to achieve a VOC content of ppm level, so the dynamic devolatilization unit selects an operating pressure within the above range.

[0072] Herein, the "dynamic" in the dynamic devolatilization unit refers to the polymer solution being in a state of tumbling up and down or in any direction inside the unit, so that the polymer surface is forced to be renewed; in contrast, the "static" in the static devolatilization unit refers to the polymer solution having no forced tumbling dynamics inside the unit except for the flow state of material transmission. In a specific example, the dynamic devolatilization unit is a screw extruder devolatilizer.

[0073] Preferably, in order to achieve a better devolatilization effect, an inert dispersant, such as nitrogen, argon, ethylene, methane, hydrogen, carbon dioxide, etc., can be introduced into one or more devices in the flash unit, the static devolatilization unit and the dynamic devolatilization unit, wherein the preferred inert dispersant is nitrogen. The dispersant is added to the equipment at a preferred mass ratio of 1:100 to 1:50 with the polymer solution to assist in the mass transfer and gasification of the volatiles. Preferably, the position where the inert dispersant is introduced is the connecting pipeline or equipment of the final static devolatilizer and / or the dynamic devolatilization unit, and ensures that the inert dispersant is fully dispersed in the high-temperature polymer. The addition of the inert dispersant can reduce the partial pressure of the volatiles, which helps the evaporation of the volatiles; and it forms foaming with the polymer solution to promote the mass transfer of the volatiles in the polymer.

[0074] In the present invention, the volatile recovery unit is used to recover polymer volatiles. Preferably, the volatile recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating. The heating temperature is 100-300°C, preferably 120-250°C. If the temperature is lower than 100°C, the entrained polymer will condense and block the pipeline due to heat dissipation. If the temperature is higher than 300°C, the polymer will be carbonized into a solid and block the pipeline. In order to ensure the simplicity of the system and prevent the pipeline from being blocked by the polymer, no additional gas-liquid separation device or condensation heat exchange equipment is set on the connected process pipeline.

[0075] Preferably, in addition to the function of recovering polymer volatiles, the volatile recovery unit can also be coupled with other functions, including but not limited to: graded absorption of volatiles; separation of absorbed volatiles, separation of light component monomers and solvents and returning them to the reactor, and enrichment of heavy components at the bottom of the tower and discharge from the system; pressure regulation of the static devolatilization unit and the dynamic devolatilization unit, etc.

[0076] In another specific example, the volatile exhaust gases of the static devolatilization unit and the dynamic devolatilization unit enter different volatile recovery units respectively, and the recovery units are distillation towers. The functions of the above coupled recovery system are achieved by controlling the pressures of the distillation towers respectively.

[0077] In order to achieve graded absorption of volatiles, the volatile recovery unit is divided into a low-pressure absorption area, a medium-pressure absorption area and a high-pressure absorption area along the axial direction according to the source pressure of the volatiles, the polymer content in the volatiles and the absorption effect. In a specific example, the volatile recovery unit is provided with at least two second volatile inlets connected to the static devolatilization unit and a third volatile inlet connected to the dynamic devolatilization unit at different axial positions. Preferably, there are multiple second volatile inlets, which are respectively connected to each static devolatilizer.

[0078] In order to separate the absorbed volatiles, in a specific example, the volatile recovery unit is an absorption separation tower, with a condenser at the top and a reboiler at the bottom. The light components such as the solvent are enriched at the top of the tower through the principle of distillation separation, and a part of it is refluxed into the tower to wash the rising gas phase to prevent the polymer from being entrained to the top of the tower, and the other part is directly extracted and circulated to the reactor. At the same time, a small amount of heavy components entrained into the tower are enriched at the bottom of the tower after washing, and low molecular weight polymers are not accumulated in the system through intermittent extraction. The uncooled high-temperature volatiles directly enter the tower, which greatly saves the energy consumption of the reboiler at the bottom of the tower, and can save energy by up to 80% compared with traditional distillation towers.

[0079] Preferably, the molar reflux ratio at the top of the tower is 0.01 to 3, and more preferably, the reflux ratio is 0.1 to 1; this reflux ratio can minimize energy consumption while ensuring separation effect.

[0080] Preferably, the extraction concentration of the low molecular weight polymer at the bottom of the tower is 1% to 50% wt, and more preferably 5% to 30% wt. The heavy components returning to the reactor in the circulating solvent will affect the reaction, but the concentration of the heavy components is actually only at the ppm level. The heavy components need to be enriched at the bottom of the separation tower, otherwise the amount of solvent discharged with the heavy components will be large, resulting in losses.

[0081] Preferably, the operating temperature of the tower bottom should be 20-30°C lower than the polymer implosion temperature.

[0082] In the present invention, the absorption separation tower can be set with different separation components and divided into different areas according to different absorption purposes, taking into account pressure drop and anti-clogging. For example, the top of the tower is set as a low-pressure absorption area, and the separation component at the top of the tower is a low-pressure drop filler such as a wire mesh or a spray absorption; the middle of the tower is set as a medium-pressure absorption area, and the separation component in the tower is an anti-clogging internal part, such as a corrugated plate filler or a sieve plate or a fixed valve tray; the bottom of the tower is set as a high-pressure absorption area, and the separation component at the bottom of the tower is a floating valve or a bubble tray. The above-mentioned separation component at the top of the tower plays the role of low pressure drop and high separation efficiency; the separation component in the tower plays the role of taking into account pressure drop and anti-clogging; the separation component at the bottom of the tower mainly prevents polymer clogging, and plays a role of large pressure drop to control the pressure of the first-stage static devolatilizer.

[0083] Preferably, the top of the absorption separation tower is operated at negative pressure, with a pressure of 0 to 10 kPaA, preferably 0 to 1 kPaA, and more preferably 0 to 0.5 kPaA; the bottom of the absorption separation tower is operated at positive pressure, with a pressure of 1 to 6 barG, preferably 2 to 5 barG, and more preferably 2 to 4 barG. The above pressure parameters match the pressures required by the corresponding static devolatilization unit and dynamic devolatilization unit.

[0084] In order to realize the pressure regulation function of the above-mentioned volatile recovery unit, in a specific example, the pressure difference between the top and bottom of the absorption separation tower is controlled by a specially designed pressure control tray in the tower, and the pressure control tray is single-stage or multi-stage. There is no need to adjust the pressure through a pressure regulating valve, which greatly simplifies the process, effectively prevents pipeline and equipment blockage, and saves investment.

[0085] Preferably, the opening rate of the pressure-controlled tray is 1% to 20%, more preferably, 3% to 16%; the preferred opening rate of the tray can effectively form the required pressure drop and better control the pressure of each section in the tower;

[0086] Preferably, each pressure-controlled tray is designed with any one, a combination of two or three of the three types of float valves, light, medium and heavy, in proportion;

[0087] Preferably, for the three float valve combinations, the quantity ratios of light: medium: heavy are 2-3: 5-6: 3-1 respectively;

[0088] The floating valves of each layer of tower plate are designed according to the above-mentioned light, medium and heavy proportions to meet the operational flexibility of the system. For example, when the load is low, only the light valve or part of the middle valve is opened, so the actual opening rate of the tower plate is not 100% as originally designed, which can ensure a certain pressure drop. When the load is high, under the heating and evaporation of the reboiler, the steam in the tower will open the middle valve and the heavy valve, thereby increasing the actual opening rate, so that the pressure drop of the tower plate can still be adjusted.

[0089] Preferably, for the three float valves, the mass ratios of light: medium: heavy are 1:2:3 respectively.

[0090] Preferably, in addition to the above-mentioned pressure-controlled tower trays for respectively adjusting the pressure of the static devolatilization unit and the above-mentioned dynamic devolatilization unit, an auxiliary pressure regulating system can also be set according to specific working conditions. In a specific example, an inert medium is introduced into the absorption separation tower for pressure regulation. The inert medium is preferably nitrogen, argon, ethylene, methane, hydrogen, carbon dioxide, etc.

[0091] Preferably, the amount of the inert medium introduced is 1% to 50% by weight, more preferably 5% to 30% by weight, of the gas phase in the tower.

[0092] Therefore, the connection points of the volatile recovery unit described in the present invention with the static devolatilization unit and the dynamic devolatilization unit can be connected at different axial positions according to the pressure requirements of the devolatilization system, and the pressure is adjusted by special internals of the recovery unit (such as a pressure-controlled tower plate). The recovery unit is equipped with built-in anti-clogging internals, which can effectively wash the polymers entrained by the volatiles, thereby ensuring efficient and stable operation of the system and greatly reducing energy consumption.

[0093] In the present invention, monomers, solvents and catalysts are loaded into a reactor, and the monomers are reacted to form a polymer. In a specific example, raw monomers ethylene and comonomers are used, and the comonomers are one or more of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene. For example, 1-octene. The solvent is an inert alkyl, such as pentane, methylpentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, hydrogenated naphtha or a combination thereof substituted C5-12 hydrocarbon, such as isoparaffin Isopar E. The catalyst used is a Ziegler-Natta catalyst, a dimetallocene catalyst, a constrained geometry catalyst, a polyvalent aromatic oxyether complex, a phosphinimine or a combination thereof. In a specific example, the polymerization reaction is an adiabatic or isothermal process, with a reaction pressure of 15 to 50 barg and a reaction temperature of 120 to 230°C.

[0094] Preferably, after the polymerization reaction is completed, the polymer solution is subjected to catalyst deactivation treatment, the deactivating agent is preferably water and alcohol, the polymer content in the reaction solution is 8% to 32% wt, and the preferred concentration is 10% to 25% wt. The polymer solution after the deactivation treatment flows into the flash unit by gravity.

[0095] A second aspect of the present invention provides a method for devolatilizing a polymer, the method comprising:

[0096] The polymer solution formed in the reactor is sent to a flash evaporation unit to flash the polymer solution to obtain a first volatile gas phase and a pre-devolatilized polymer solution;

[0097] The pre-devolatilization polymer solution from the flash unit is sent to a static devolatilization unit, and the pre-devolatilization polymer solution is heated by at least two stages of static devolatilizers connected in series arranged inside the static devolatilization unit to obtain a second volatile gas phase and a static devolatilization polymer solution;

[0098] The static devolatilization polymer solution from the static devolatilization unit is sent to the dynamic devolatilization unit, and the static devolatilization polymer solution is heated in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution;

[0099] The second volatile gas phase in the static devolatilization unit and the third volatile gas phase in the dynamic devolatilization unit are sent to a volatile recovery unit;

[0100] The first volatile gas phase includes unreacted light component monomers in the polymer solution, the second volatile gas phase includes the solvent in the polymer solution, and the third volatile gas phase includes the heavy components in the polymer solution.

[0101] Preferably, the method further comprises: preheating the pre-devolatilization polymer solution from the flash unit and then feeding it into the static devolatilization unit.

[0102] Preferably, the volatile matter recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating.

[0103] Preferably, the interior of the volatile recovery unit is axially divided into a low-pressure absorption area, a medium-pressure absorption area and a high-pressure absorption area to perform graded absorption of volatile components; and the polymer volatile solvent removed by the static devolatilization unit is fed into the volatile recovery unit through the second volatile inlet, and the polymer volatile heavy components removed by the dynamic devolatilization unit are fed into the volatile recovery unit through the third volatile inlet.

[0104] Preferably, the method further comprises: separating the components in the volatiles by a separation member arranged inside the volatile recovery unit to obtain light component monomers, heavy components and solvents respectively.

[0105] Preferably, the method further comprises: the volatile matter recovery unit performs pressure control on the static devolatilization unit and the dynamic devolatilization unit.

[0106] Preferably, the method further comprises: sending the first volatile gas phase in the flash unit into the reactor.

[0107] Preferably, the polymer solution is quenched to deactivate the catalyst before being fed into the flash unit.

[0108] The process flow and specific parameters in the above method are described in the above system section and will not be repeated here.

[0109] The present invention is further described below with detailed exemplary embodiments, but these embodiments do not constitute any limitation to the present invention.

[0110] Example 1

[0111] See also Figure 1 An embodiment of the present invention provides a system for devolatilizing a polymer, the system comprising a flash unit 102 , a static devolatilization unit 103 , a dynamic devolatilization unit 104 and a volatile matter recovery unit 105 .

[0112] The flash unit 102 is located downstream of the reactor 101. The polymer solution after quenching in the reactor flows into the flash unit 102 by gravity. The flash unit 102 is a vertical or horizontal flash tank. Under a positive pressure of about 10.3 barG, the unreacted low-boiling point raw material monomer is removed by adiabatic flash evaporation;

[0113] Anti-mist entrainment internal parts are arranged inside or outside the flash tank near the first gas phase outlet. To further reduce mist entrainment and ensure the stable operation of the circulating booster equipment, the gas velocity of the first volatile gas phase such as low-boiling point polymerization monomer in the flash tank is ≤12m / s, and the first volatile gas phase is directly delivered to the reactor through the compressor 201 without condensation.

[0114] The flash unit 102 is connected to the static devolatilization unit 103 including a multi-stage static devolatilizer through the pipeline 306. The polymer solution from which the first volatile gas phase is removed is pressurized by a booster pump and sent to the split heat exchanger 202 before the first-stage static devolatilizer 203 for preheating. The preheated polymer solution sequentially passes through the multi-stage static devolatilizers in series. Each stage of the static devolatilizer is connected by a process pipeline, a delivery pump and a heat exchange device, wherein each static devolatilizer has a lower or equal pressure than the previous stage of the static devolatilizer. After the polymer passes through the multi-stage static devolatilizer, the volatile matter is reduced to a mass fraction of less than 5%;

[0115] The polymer concentrated by the static devolatilization unit 103 is transported to the dynamic devolatilization unit 104 via a gear pump. The dynamic devolatilization unit forces the polymer to undergo surface renewal through its internal dynamic components, accelerates the mass transfer rate of volatile components, and removes trace amounts of non-volatile components from the polymer under near-vacuum conditions through its own heating system. Finally, the volatile content in the polymer reaches 50 to 1000 ppm.

[0116] The volatile recovery unit 105 is directly connected to the multi-stage static devolatilizer and the dynamic devolatilization unit 104 through a pipeline with heating (307, 309, 312, 314), and each connection point is connected to different axial positions of the volatile recovery unit 105 according to the pressure requirements of the devolatilization unit.

[0117] The volatile recovery unit 105 is an absorption separation tower with a multifunctional coupling function. The light component monomers and solvents in the recovered volatiles are separated and sent back to the reactor through the pipeline 318, and the heavy components are enriched at the bottom of the tower and discharged from the system through the pipeline 315. The pressure at the top of the tower is controlled by the vacuum pump 211, and the pressure in the tower is mainly adjusted by the pressure control tray 210.

[0118] In this embodiment, the pressure control tray 210 is two-stage. The opening rate of the pressure control tray is about 12%; each layer of the pressure control tray is designed with three combinations of light, medium and heavy float valves according to proportion; wherein the mass ratio of the three float valves, light: medium: heavy, is 1:2:3 respectively.

[0119] In this embodiment, the top of the absorption separation tower is set as a low-pressure absorption area, and the separation unit at the top of the tower is a low-pressure drop filler such as a wire mesh or a spray absorption; the middle of the tower is set as a medium-pressure absorption area, and the separation unit in the tower is an anti-clogging internal part, such as a corrugated plate filler or a sieve plate or a fixed valve tower tray; the bottom of the tower is set as a high-pressure absorption area, and the separation unit at the bottom of the tower is a float valve or a bubble tower tray.

[0120] In this embodiment, the polymer solution discharged from the reactor 101 by gravity has a flow rate of 1200 kg / h, a temperature of 200° C., a pressure of about 49.7 barG, and a mass composition of about 16% POE, about 78% solvent, about 1% ethylene, and about 5% octene. The polymer solution enters the flash unit 102 for flash evaporation at a pressure of about 11.3 barG, where low-boiling ethylene is removed. The removed ethylene is not collected by condensation and is directly sent back to the reactor 101 through the compressor 201. In another embodiment, because the amount of flash ethylene is small, the unreacted ethylene can also be directly discharged for treatment. The polymer solution from which low-boiling ethylene is removed is sent to the split heat exchanger 202 for heating via a booster pump, and the temperature is about 260°C. The heated fluid enters the first-stage static devolatilizer for devolatilization. To prevent entrainment of mist, the gas phase flow rate in the static devolatilizer is controlled to be less than 15m / s. The separated volatiles enter the bottom of the volatile recovery unit 105 via pipeline 307, and the operating pressure of the first-stage static devolatilizer is controlled to be about 2.2barG. The polymer is concentrated to about 65%wt here. The first-stage concentrated liquid is sent to the second-stage static devolatilizer 204 via a gear pump. The connected heat exchanger 205 located at the top of the second-stage static devolatilizer heats the polymer to about 257°C. The heated high-viscosity fluid enters the second-stage static devolatilizer for devolatilization. The separated volatiles enter the middle of the volatile recovery unit 105 via pipeline 309, and the operating pressure of the second-stage static devolatilizer is controlled to be about 50kPaA. The polymer is concentrated to about 85%wt here. The secondary concentrated liquid is sent to the third-stage static devolatilizer 206 through a gear pump. The connected heat exchanger 207 located at the top of the third-stage static devolatilizer heats the polymer to about 259°C. The heated high-viscosity fluid enters the third-stage static devolatilizer for devolatilization. The separated volatiles enter the top of the volatile recovery unit 105 through the pipeline 312, and the operating pressure of the third-stage static devolatilizer is controlled to be about 0.55 kPaA. The polymer is concentrated to about 97.5%wt here. The concentrated high-concentration polymer is sent to the dynamic devolatilization unit 104 through a gear pump. In this embodiment, the dynamic devolatilization unit is specifically a screw extrusion devolatilizer. The extruder has its own heating system. High-temperature hot oil is passed into the outer sleeve and the hollow shaft. The hot oil temperature is about 310°C. The volatiles removed by the screw extrusion devolatilizer enter the volatile recovery unit 105 through the pipeline 314, and the pressure is controlled to be about 0.55 kPaA. The polymer is concentrated to about 99.97%wt here.

[0121] In this embodiment, the volatile recovery unit 105 is directly connected to the second volatile gas phase outlet at the top of the static devolatilization unit 103 and the third volatile gas phase outlet of the dynamic devolatilization unit 104 through the heating pipeline (307, 309, 312, 314), and is continuously operated for 30 days without clogging of the pipeline and equipment, and the pressure drop of the connecting pipeline is less than 10kPa. In this embodiment, the volatile recovery unit 105 is specifically an absorption separation tower 209, the operating pressure at the top of the tower is about 0.4kPaA, the operating pressure at the bottom of the tower is about 2barG, the reflux ratio at the top of the tower is about 0.5, the alkane solvent separated and purified at the top of the tower is pumped back to the reactor 101, and the entrained low molecular weight polymer is intermittently produced at the bottom of the tower, and the polymer production concentration is 15-50%wt.

[0122] Example 2

[0123] Similar to Example 1, except that: the flash unit 102 is a horizontal flash tank, and the unreacted low-boiling point raw material monomer is removed by adiabatic flash evaporation under a positive pressure of about 9.8 barG; the first volatile gas phase such as the low-boiling point polymer monomer has a gas velocity of ≤10 m / s in the flash tank;

[0124] In this embodiment, the polymer solution discharged from the reactor 101 by gravity has a flow rate of 2000 kg / h, a temperature of 187° C., a pressure of 48 barG, and a mass composition of about 20% POE, about 75% solvent, about 1% ethylene, and about 4% octene. The polymer solution enters the flash unit 102 for flash evaporation at a pressure of 9.8 barG, where low-boiling ethylene is removed. The removed ethylene is not collected by condensation and is directly sent back to the reactor 101 through the compressor 201. In another embodiment, because the amount of flash ethylene is small, the unreacted ethylene can also be directly discharged for treatment. The polymer solution from which low-boiling ethylene is removed is sent to the split heat exchanger 202 for heating via a booster pump, and the temperature is about 255°C. The heated fluid enters the first-stage static devolatilizer for devolatilization. To prevent entrainment of mist, the gas phase flow rate in the static devolatilizer is controlled to be less than 20m / s. The separated volatiles enter the bottom of the volatile recovery unit 105 via pipeline 307, and the operating pressure of the first-stage static devolatilizer is controlled to 2.8barG. The polymer is concentrated to about 57%wt here. The first-stage concentrated liquid is sent to the second-stage static devolatilizer 204 via a gear pump. The connected heat exchanger 205 located at the top of the second-stage static devolatilizer heats the polymer to about 240°C. The heated high-viscosity fluid enters the second-stage static devolatilizer for devolatilization. The separated volatiles enter the middle of the volatile recovery unit 105 via pipeline 309, and the operating pressure of the second-stage static devolatilizer is controlled to 0.9barA. The polymer is concentrated to about 83.6%wt here. The secondary concentrated liquid is sent to the third-stage static devolatilizer 206 through a gear pump. The connected heat exchanger 207 located at the top of the third-stage static devolatilizer heats the polymer to about 258°C. The heated high-viscosity fluid enters the third-stage static devolatilizer for devolatilization. The separated volatiles enter the top of the volatile recovery unit 105 through the pipeline 312, and the operating pressure of the third-stage static devolatilizer is controlled to be about 0.7 kPaA. The polymer is concentrated to about 95.2%wt here. The concentrated high-concentration polymer is sent to the dynamic devolatilization unit 104 through a gear pump. In this embodiment, the dynamic devolatilization unit is specifically a screw extrusion devolatilizer. The extruder has its own heating system. High-temperature hot oil is passed into the outer sleeve and the hollow shaft. The hot oil temperature is about 300°C. The volatiles removed by the screw extrusion devolatilizer enter the volatile recovery unit 105 through the pipeline 314, and the pressure is controlled to be about 0.7 kPaA. The polymer is concentrated to about 99.934%wt here.

[0125] In this embodiment, the volatile recovery unit 105 is directly connected to the second volatile gas phase outlet at the top of the static devolatilization unit 103 and the third volatile gas phase outlet of the dynamic devolatilization unit 104 through the heating pipeline (307, 309, 312, 314), and it is operated continuously for 42 days without blocking the pipeline and equipment, and the pressure drop of the connecting pipeline is less than 10kPa. In this embodiment, the volatile recovery unit 105 is specifically an absorption separation tower 209, the operating pressure at the top of the tower is about 0.5kPaA, the operating pressure at the bottom of the tower is about 2.4barG, the reflux ratio at the top of the tower is about 1, the alkane solvent separated and purified at the top of the tower is pumped back to the reactor 101, and the entrained low molecular weight polymer is intermittently produced at the bottom of the tower, and the polymer production concentration is 30-32%wt.

[0126] Comparative Example 1

[0127] See also Figure 2 The polymer solution discharged from the reactor 101 by gravity has a flow rate of about 1000 kg / h, a temperature of 200°C, a pressure of about 48 barG, and a mass composition of about 15% POE, about 79% solvent, about 1% ethylene, and about 5% octene. The polymer solution enters the flash unit 102 for flash evaporation at a pressure of about 10.5 barG, where low-boiling ethylene is removed. The removed ethylene is not collected by condensation and is directly sent back to the reactor 101 through the compressor 201. The polymer solution from which low-boiling-point ethylene has been removed is sent to the split heat exchanger 202 for heating via a booster pump to a temperature of about 262°C. The heated fluid enters the first-stage static devolatilizer for devolatilization. To prevent entrainment of mist, the gas phase flow rate in the devolatilizer is controlled to be less than 15 m / s. The separated volatiles enter the condenser 212 for cooling, and the liquid phase enters the liquid volatile collection tank 216. The operating pressure of the first-stage static devolatilizer is controlled at about 1.8 barG by a regulating valve on the pipeline 307, and the polymer is concentrated to about 71% wt here. The primary concentrated liquid is sent to the secondary static devolatilizer 204 through a gear pump. The connected heat exchanger 205 located on the top of the secondary static devolatilizer heats the polymer to about 240°C. The heated high-viscosity fluid enters the secondary static devolatilizer 204 for devolatilization. The separated volatiles enter the condenser 213 for cooling, and the liquid phase enters the liquid volatile collection tank 216. The operating pressure of the secondary static devolatilizer is controlled at about 0.5 kPaA by the regulating valve on the pipeline 309. The polymer is concentrated to about 95.7%wt here. The concentrated high-concentration polymer is sent to the dynamic devolatilization unit 104 through a gear pump. In the present embodiment, the dynamic devolatilization unit is specifically a screw extruder devolatilizer. The extruder has its own heating system. High-temperature hot oil is introduced into the external sleeve and the hollow shaft. The hot oil temperature is about 295°C. The volatile matter removed by the screw extruder devolatilizer enters the condenser 214 for cooling, and the liquid phase enters the liquid phase volatile matter collection tank 216. The pressure is controlled to be about 0.5 kPaA by a vacuum device. The polymer is concentrated to about 99.9%wt here.

[0128] In this embodiment, the volatile recovery unit 105 is connected to the liquid volatile collection tank 216 via a pipeline, wherein the liquid solvent is sent to the bottom of the separation tower 209 via a pump 217. After the system has been running continuously for 16 days, the pipelines (307, 309) and the condensers (212, 213) are blocked to varying degrees, the operating pressure of the multi-stage static devolatilization unit 103 increases by 10 to 50 kPa, and the outlet polymer concentration fluctuates to 87 to 94% wt. After the dynamic devolatilization unit 104 devolatilizes, the POE polymer volatile content obtained at the outlet is 1500ppm to 8400ppm, and the VOC after granulation is unqualified. After continuing to run for 2 days, the pressure of the multi-stage static devolatilization system 103 increased significantly, and the device was shut down for cleaning.

[0129] By comparing this comparative example with the embodiments, the volatile matter recovery system in Example 1 can effectively control the pressure of different devolatilization units through the design of anti-clogging internals and pressure-controlled tower plates, and ensure that the recovery system is not easily blocked during the washing and recovery of volatiles. The device in Example 1 operates stably for 30 days, and the polymer concentration is stably maintained at about 99.97%wt; the device in Example 2 operates stably for 42 days, and the polymer concentration is stably maintained at about 99.934%wt; the device in Comparative Example 1 operates for 16 days, and the pressure of the devolatilization unit increases due to system blockage, and the polymer concentration drops from about 99.9%wt to 87-94%wt; it can be seen that different settings of the volatile matter recovery system will result in different volatile matter recovery effects and device operation stability.

[0130] Comparative Example 2

[0131] Similar to Example 1, except that: the operating pressure of the flash unit 102 is 6 barG, and the ethylene in the flash gas phase carries a large amount of solvent (solvent amount> 30%), resulting in frequent tripping of the compressor 201 due to liquid.

[0132] Comparative Example 3

[0133] Similar to Example 1, except that: the polymer solution from which low-boiling ethylene has been removed is heated to about 280° C. and enters the first-stage static devolatilizer 203, the operating pressure is 0.09 barG, the gas phase flow rate is about 25 m / s, and the separated volatiles enter the bottom of the volatile recovery unit 105 through pipeline 307, and the heating temperature of pipeline 307 is 95° C. After the device was operated for 20 days, pipeline 307 was blocked, the pressure of the first-stage static devolatilizer 203 rose to 5.4 barG, the devolatilization effect became poor, and the outlet polymer concentration dropped from 75% to 40%wt.

[0134] Comparative Example 4

[0135] Similar to Example 1, the difference is that: the connected heat exchanger 205 at the top of the secondary static devolatilizer heats the polymer to about 307°C, the operating pressure of the secondary static devolatilizer is about 50kPaA, and the polymer is concentrated to about 91%wt here; the connected heat exchanger 207 at the top of the tertiary static devolatilizer heats the polymer to about 310°C, the operating pressure is about 0.5kPaA, and the polymer is concentrated to about 98.7%wt here. The concentrated high-concentration polymer is sent to the dynamic devolatilization unit 104 through a gear pump, the hot oil temperature is about 330°C, the pressure is about 0.5kPaA, and the polymer is concentrated to about 99.99%wt here. However, the final polymer product was analyzed and found to be degraded and the color number was high, and the product was unqualified.

[0136] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are within the spirit scope of the present invention.

Claims

1. A system for devolatilization of polymers, characterized in that: The system includes: a flash unit, located downstream of a reactor for forming a polymer, for receiving and flashing a polymer solution from the reactor to obtain a first volatile gas phase and a pre-devolatilized polymer solution; a static devolatilization unit, located downstream of the flash unit, comprising at least two stages of static devolatilizers connected in series, for receiving and heating the pre-devolatilized polymer solution from the flash unit to obtain a second volatile gas phase and a static devolatilized polymer solution; A dynamic devolatilization unit, located downstream of the static devolatilization unit, is used to receive the static devolatilization polymer solution from the static devolatilization unit and heat it in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution; A volatile recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit, and is used to receive the second volatile gas phase and the third volatile gas phase; the interior of the volatile recovery unit is divided into a low-pressure absorption area, a medium-pressure absorption area and a high-pressure absorption area along the axial direction; a separation component is arranged inside the volatile recovery unit, and is used to separate the components in the volatiles to obtain light component monomers, heavy components and solvents respectively; the volatile recovery unit is connected to the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating, and the heating temperature is 100-300°C; The first volatile gas phase includes unreacted light component monomers in the polymer solution, the second volatile gas phase includes the solvent in the polymer solution, and the third volatile gas phase includes the heavy components in the polymer solution.

2. The polymer devolatilization system according to claim 1, characterized in that: The system further comprises: a preheating unit located between the flash unit and the static devolatilization unit, and used for preheating the pre-devolatilization polymer solution from the flash unit and then sending it to the static devolatilization unit.

3. The polymer devolatilization system according to claim 1 or 2, characterized in that: A first heating device is provided inside the static devolatilizer for heating the pre-devolatilization polymer solution entering the static devolatilization unit; and / or, The dynamic devolatilization unit includes a dynamic component for churning the polymer solution and a second heating device for heating the polymer solution.

4. The polymer devolatilization system according to claim 1, characterized in that: At least two second volatile component inlets communicated with the static devolatilization unit and a third volatile component inlet communicated with the dynamic devolatilization unit are arranged at different axial positions of the volatile component recovery unit.

5. The polymer devolatilization system according to claim 1, characterized in that: In the flash unit, the first volatile gas phase enters the reactor.

6. A method for devolatilizing a polymer, characterized in that: Utilizing the system according to any one of claims 1 to 5, the method comprises: The polymer solution formed in the reactor is sent to a flash evaporation unit to flash the polymer solution to obtain a first volatile gas phase and a pre-devolatilized polymer solution; The pre-devolatilization polymer solution from the flash unit is sent to a static devolatilization unit, and the pre-devolatilization polymer solution is heated by at least two stages of static devolatilizers connected in series arranged inside the static devolatilization unit to obtain a second volatile gas phase and a static devolatilization polymer solution; The static devolatilization polymer solution from the static devolatilization unit is sent to the dynamic devolatilization unit, and the static devolatilization polymer solution is heated in a tumbling state to obtain a third volatile gas phase and a dynamic devolatilization polymer solution; The second volatile gas phase in the static devolatilization unit and the third volatile gas phase in the dynamic devolatilization unit are sent to a volatile recovery unit; The first volatile gas phase includes unreacted light component monomers in the polymer solution, the second volatile gas phase includes the solvent in the polymer solution, and the third volatile gas phase includes the heavy components in the polymer solution.

7. The method for devolatilization of a polymer according to claim 6, characterized in that: The method further comprises: preheating the pre-devolatilization polymer solution from the flash unit and then sending it to the static devolatilization unit, the preheating temperature of which is 150-300°C.

8. The method for devolatilization of a polymer according to claim 7, characterized in that: Preheating temperature: 200~260℃.

9. The method for devolatilization of a polymer according to claim 6, characterized in that: In a multi-stage static devolatilizer connected in series, according to the material flow direction, the operating pressure of the first-stage static devolatilizer is a positive pressure of 0.1 to 6 barG, and the polymer content at the outlet of the first-stage static devolatilizer is 50% to 80%; the operating pressure of the last-stage static devolatilizer is a negative pressure of 0.1 to 95 kPaA, and the polymer content of the last-stage static devolatilizer is 85% to 99.9%; and / or, The pre-devolatilization polymer solution is heated to a temperature of 150-300° C. in the static devolatilization unit; and / or, The static devolatilization polymer solution is heated to a temperature of 160-300° C. in the dynamic devolatilization unit; and / or, The operating pressure in the dynamic devolatilization unit is 0.001-1 kPaA; and / or, The volatile matter recovery unit is connected with the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating, and the heating temperature is 100-300°C.

10. The method for devolatilization of a polymer according to claim 9, characterized in that: The operating pressure of the first-stage static devolatilizer is a positive pressure of 2 to 4 barG; the operating pressure of the final-stage static devolatilizer is a negative pressure of 0.1 to 5 kPaA; and / or, The temperature of the pre-devolatilized polymer solution is heated to 180-260° C. in the static devolatilization unit; and / or, The temperature of the static devolatilization polymer solution is heated to 180-260° C. in the dynamic devolatilization unit; and / or, The operating pressure in the dynamic devolatilization unit is 0.1-1 kPaA; and / or, The volatile matter recovery unit is connected with the static devolatilization unit and the dynamic devolatilization unit through a pipeline with heating, and the heating temperature is 120-250°C.

11. The method for devolatilization of a polymer according to claim 6, characterized in that: The method further comprises: separating the components in the volatiles by a separation member disposed inside the volatile recovery unit to obtain light component monomers, heavy components and solvents respectively; and / or, The method further comprises: the volatile matter recovery unit performs pressure control on the static devolatilization unit and the dynamic devolatilization unit; and / or, The method further includes: sending the first volatile gas phase in the flash unit into the reactor.

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