Screening assembly and method for screening polymer from effluent stream with reduced polymer entrainment levels

Abstract

A method of screening polymer from a lean polymer vapor stream, wherein the method comprises the steps of: separating an effluent stream comprising polymer and a first hydrocarbon mixture into a rich polymer stream and a lean polymer vapor stream; injecting a condensed vapor composition comprising a second hydrocarbon mixture into the lean polymer vapor stream via a condensed vapor composition stream; screening a screened condensed vapor composition stream comprising polymer and condensed vapor composition from the lean polymer vapor stream.

Description

Technical Field

[0001] This invention relates to a screening assembly for screening polymers from an effluent stream removed from a polymer reactor. Furthermore, this invention relates to a method for separating polymers from the aforementioned effluent stream. In particular, the screening assembly and method can be used in solution polymerization methods. Background Technology

[0002] Typically, in solution polymerization methods, the reactor is operated at a relatively low polymer concentration. Therefore, the low polymer concentration is generally considered to be less than 30% by weight relative to the total amount of the polymer and hydrocarbon mixture, such as monomers, optional comonomers, and the solvent used.

[0003] Furthermore, reactors in solution polymerization processes are typically operated at higher temperatures than those in gas-phase polymerization. The advantage of higher temperatures is higher catalyst activity, resulting in better catalytic efficiency. However, a disadvantage is the risk of uncontrolled reactions if the exothermic reaction is rapid, as excessive heat can be absorbed into the reaction mixture. To control this rapid exothermic reaction and potential for uncontrolled reactions, polymer concentrations are typically kept between 15% and 25% by weight, thus ensuring controlled exothermic processes.

[0004] Therefore, the resulting effluent streams include individual quantities of unwanted hydrocarbons and hydrocarbon mixtures, such as solvents and unreacted monomers and optional comonomers, which must be removed from the polymer in process steps following the polymerization reaction steps.

[0005] Although solution polymerization methods known in the art differ in these subsequent process steps, almost all of these methods generally use the following steps: a) heating the polymer melt solution under pressure and b) reducing the solution pressure to allow volatile compounds to evaporate.

[0006] Typically, this solution polymerization method is carried out under conditions where the reactor pressure is above 50 barg and the temperature at the reactor outlet is above 150°C. In some solution polymerization techniques known from the prior art, in a subsequent step, the solution stream is heated to above 200°C and then the pressure is reduced to a vacuum level to produce the final polymer.

[0007] Typically, this separation occurs in a flash separator, forming a condensate stream and a vapor stream. In typical reactor assemblies or methods, this vapor stream from the evaporation step is condensed and conveyed to a recovery section. For example, this vapor stream can be reused as a source of solvent and / or non-reactive monomers and / or comonomers.

[0008] In certain applications of polymers, exceptionally low levels of volatiles are required. These volatiles can be represented, among other things, by solvent molecules and / or unreacted monomers or comonomers remaining in the polymer being produced. To achieve such low volatile levels in polymers, multi-step evaporation methods have been developed. In particular, it is known from the art that, in most cases, at least two or three steps of evaporation are required to achieve acceptablely low levels of volatiles for certain market applications of polymers, supplemented by additional equipment, such as a devolatile extruder or kneader as a final step.

[0009] Typically, in each step of a multi-step method, the vapor stream is subsequently condensed and can be reused as reactor feed for the method or conveyed to a recovery section, where hydrocarbon mixtures, such as solvents, comonomers, and monomers, are pre-separated. Summary of the Invention

[0010] Problems to be solved

[0011] These vapor streams may contain polymers that entrain the vapor stream during the separation step. Because the pressure drop in the separation step is typically large, and separation occurs so rapidly, fine polymer particles may be extracted by the evaporated material and introduced into the vapor stream. Polymer entrainment has proven to occur at high levels, particularly in the separation step. This is likely because the amount of evaporated material is greatest during the separation step.

[0012] After one or more separation steps, fouling in the equipment can lead to reduced heat removal and decreased separation efficiency of the process section / equipment. This is particularly problematic for condensers used to condense the vapor stream in subsequent steps. Fouling can significantly reduce the heat removal efficiency of such condensers. Therefore, in cases where the vapor stream is repeatedly used as reactor feed, fouling in the equipment can even affect temperature control and plant capacity in the polymerization process. Therefore, appropriate protection against the fouling effects of polymer entrainment in the vapor stream during the polymerization process, particularly after solution polymerization in the vapor / condensate phase separation step, is needed.

[0013] Purpose of the invention

[0014] In view of the above problems, one object of the present invention is to provide a screening assembly comprising a separation device, particularly a vapor phase / condensate phase separation device, for separating effluent streams, for example from a polymerization reactor, particularly from a solution polymerization reactor, containing effluent streams containing reduced or preferably eliminated polymer entrainment into one or more separated vapor phases.

[0015] Furthermore, in view of the above-mentioned problems, a second object of the present invention is to provide a method for separating an effluent stream (e.g. from a polymerization method, particularly from a solution polymerization method) into a vapor stream and a condensate stream, thereby reducing or preferably eliminating polymer entrainment into the vapor stream. Summary of the Invention

[0017] It has now been surprisingly discovered that the above objective can be achieved by combining the separation step with at least one first screening step, wherein the vapor phase of the separation step is introduced into the first screening step, and a condensed phase containing a hydrocarbon mixture is injected into the vapor stream taken out from the separation step before the vapor stream enters the first screening step.

[0018] Therefore, the present invention relates to a method for separating a polymer from an effluent comprising a polymer and a first hydrocarbon mixture, wherein the method comprises the following steps:

[0019] A) Separate the outflow stream into a polymer-rich stream and a polymer-lean vapor stream;

[0020] B) Injecting a stream of condensed vapor composition containing a condensed vapor composition of a second hydrocarbon mixture into the lean polymer vapor stream;

[0021] C) Sieve the lean polymer vapor stream to obtain a sieved condensed vapor composition stream containing the polymer and the condensed vapor composition.

[0022] Furthermore, the present invention relates to a screening assembly comprising a separation device fluidly connected to a conduit for an effluent stream comprising a polymer and a hydrocarbon mixture, wherein the separation device is configured to separate the effluent stream into a polymer-rich stream and a polymer-lean vapor stream, wherein the separation device includes an inlet, a first outlet for removing the polymer-rich stream and a second outlet for removing the polymer-lean vapor stream, a first screening device being connected to the second outlet of the separation device via a conduit for the polymer-lean vapor stream, wherein the first screening device is configured to inject a condensed vapor composition comprising a hydrocarbon mixture into the polymer-lean vapor stream via a conduit for a condensed vapor composition stream, and to screen out a condensed vapor composition stream comprising polymer and the condensed vapor composition from the polymer-lean vapor stream, wherein the first screening device includes an inlet, a first outlet for removing the condensed phase and a second outlet for removing the vapor phase.

[0023] Finally, the present invention relates to the use of such a screening assembly to reduce scaling in polymerization methods, preferably solution polymerization methods.

[0024] definition

[0025] The term "jetting" as used herein must be understood as a method step in which a condensed phase is introduced into a gas phase. This results in the condensed phase being broken into multiple droplets. This is typically accomplished by at least one nozzle. Jetting must also be understood as a method step in which a two-phase system (gas / condensate) with the highest possible phase separation surface is formed.

[0026] The term "condensation point" as used herein must be understood as a combination of conditions that cause a compound to condense from a vaporized mixture. Specifically, the condensation point depends on the system's pressure and temperature. The condensation point can be achieved by changing one or both of these parameters.

[0027] The terms "volatiles" or "volatile compounds" as used herein must be understood to mean compounds with significantly lower molecular weights compared to the polymers produced in the methods of this invention. Such compounds are typically present in gaseous form when exposed to a flash separator. Typically, the volatile compounds are mixtures of volatile hydrocarbons. Preferably, the volatile hydrocarbon mixture comprises at least one unreacted monomer, optionally an unreacted comonomer, a solvent, and any other gaseous components present in the effluent stream.

[0028] Flash separators (also known as low-pressure separators) have been known in the art for decades. As is well known in the art, a liquid feed is conveyed to a flash vessel operating under reduced pressure. A portion of the liquid phase evaporates and can be removed from the low-pressure separator as an overhead stream (or vapor stream). The portion remaining in the liquid phase is then removed from the flash vessel as a bottom stream or liquid stream. This process is described by operating the low-pressure separator under conditions where both gas and liquid phases are present simultaneously in the flash vessel.

[0029] The gravity separator used in this paper includes a container in which a two-phase (gas / solid) system can be separated. The gas phase with a lower relative density (the polymer-lean phase) is removed from the top of the container, while the solid phase with a higher relative density (the polymer-rich phase in this example) is removed from the bottom of the container.

[0030] The term separation efficiency used in this paper is defined as the mass flow rate of the component taken from the lean polymer stream or vapor stream divided by the (theoretical) mass flow rate of the component in the lean polymer stream or condensate stream under equilibrium conditions.

[0031] As used in this article, the term "sieving" refers to a method of partially or completely removing solids from a fluid. Attached Figure Description

[0032] Figure 1 shows a schematic diagram of a screening assembly and method including a cyclone separator and a subsequent filter according to a first preferred embodiment of the present invention.

[0033] Figure 2 shows a schematic diagram of a screening assembly and method including a first screening device according to a second preferred embodiment of the present invention, wherein the vapor stream from the second outlet of the first screening device is condensed and reintroduced into the airflow entering the first screening device by injection.

[0034] Figure 3 shows a schematic diagram of a screening component and method according to a third preferred embodiment of the present invention, representing a combination of the first and second preferred embodiments shown in Figures 1 and 2.

[0035] Figure Labels

[0036] 1 Polymerization reactor

[0037] 2 Separation device

[0038] 3 First screening device

[0039] 4. Second screening device

[0040] 5. Condensed vapor composition container

[0041] 6 First Pump

[0042] 7 Condenser

[0043] 8. Filtered condensate vapor stream container

[0044] 9 Second Pump

[0045] a. Outflow stream (leaving the polymerization reactor (1))

[0046] b Polymer-rich flow

[0047] c. Polymer-poor vapor flow

[0048] d Condensed vapor composition stream

[0049] e. Steam stream from the first sieve

[0050] f-screened condensed vapor composition stream

[0051] g condensed steam cleaning flow

[0052] The steam flow of the second sieve.

[0053] i. Filtered condensed vapor stream

[0054] The vapor stream of spray condensation

[0055] k-Filtered condensed steam cleaning stream Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and embodiments therein.

[0057] The screening assembly according to the present invention

[0058] In the most general embodiment of the present invention, a screening component is provided, comprising:

[0059] A separation device (2) is fluidly connected to a conduit for an outflow stream (a), the outflow stream comprising a mixture of polymer and hydrocarbon, wherein the separation device (2) is configured to separate the outflow stream (a) into a polymer-rich stream (b) and a polymer-lean vapor stream (c), wherein the separation device (2) includes an inlet, a first outlet for removing the polymer-rich stream (b) and a second outlet for removing the polymer-lean vapor stream (c).

[0060] A first screening device (3) is connected to a second outlet of the separation device (2) via a pipe for a lean polymer vapor stream (c), wherein the first screening device (3) is configured to inject a condensed vapor composition containing a hydrocarbon mixture into the lean polymer vapor stream (c) via a pipe for a condensed vapor composition stream (d), and to screen out a condensed vapor composition stream (f) containing polymer and the condensed vapor composition from the lean polymer vapor stream (c), wherein the first screening device (3) includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase. Preferably, the hydrocarbon mixture comprises a solvent, unreacted monomers, and / or comonomers.

[0061] Preferably, the vapor stream generated in the separation device (2) is superheated. This is due to the conditions typically used in such separation steps. Preferably, the temperature used in the separation device (2) is 100°C to 400°C, more preferably 130°C to 300°C, and even more preferably 170°C to 250°C. Furthermore, the pressure drop associated with the pressure in the outflow stream (a) is preferably greater than 30 barg, more preferably greater than 60 barg, and most preferably greater than 90 barg. Therefore, the conditions found in the lean polymer vapor stream (c) are set as a mixture of hydrocarbons, i.e., solvent, unreacted monomers and / or comonomers, not at their condensation point. Therefore, the mixture of compounds in the lean polymer vapor stream (c) is preferably present in gaseous form.

[0062] It has now been found that by injecting a condensed vapor composition containing a hydrocarbon mixture into a polymer-lean vapor stream (c), entrainment in the first screening vapor stream of the first screening device can be significantly reduced. Without being bound by theory, it is thought that the condensed phase adheres to the polymer particles and makes them heavier. Therefore, fewer polymer particles are entrained into the gas phase. Furthermore, the high temperature of the condensed phase prevents high-concentration polymers from "adhering" to the walls or interior of the device. It is further believed that the injection has two effects. First, the condensed phase itself already provides the aforementioned effects. Second, it cools the mixture in the polymer-lean vapor stream (c) to its eventual condensation point. Therefore, even more condensed phase is generated, further enhancing the effect of reducing entrainment.

[0063] Preferably, the effluent is removed from the polymerization reactor (1), and more preferably from the solution polymerization reactor.

[0064] Preferably, the separation device (2) can be any separation device suitable for separating the effluent from the polymerization reactor into a polymer-lean vapor stream and a polymer-rich stream. More preferably, the separation device (2) is a flash separator.

[0065] Similarly, the first screening device (3) can be any screening device suitable for screening the polymer in the polymer-lean vapor stream (c) of the separation device (2) from the gaseous components in the gas stream. Preferably, the first screening device (3) is configured for gravity separation. More preferably, the first screening device (3) is a cyclone separator. Since it has been shown that polymer entrainment remains high after the separation step, i.e. after the separation device (2), gravity separation, especially cyclone separators, has been found to be the most efficient in terms of separation efficiency.

[0066] In another preferred embodiment of the invention, the first screening device (3) is a filter. In one embodiment of the invention, the filter (4) includes a flake clarifier. In another embodiment of the invention, the filter (4) includes a demister. In a further preferred embodiment, the filter (4) includes a flake clarifier and a demister. Most preferably, the flake clarifier and the demister are positioned such that the demister is used after the flake clarifier.

[0067] Flake clarifiers have two advantages. First, their compact design saves more than 85% of space compared to traditional sedimentation tanks. Second, they have no moving parts. Therefore, they require almost no maintenance and are a low-energy-consumption system.

[0068] The advantage of demisters lies in their applicability to all gas-liquid flow regimes across a wide range of gas velocity ranges. Demisters generally have a simple structure and a large surface area. However, they also cause a low pressure drop.

[0069] It was found that having only one first screening device was not efficient enough in removing entrained polymers. Therefore, in a preferred embodiment, the screening assembly further includes a second screening device (4), which includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase.

[0070] The second screening device (4) connected in parallel with the first screening device (3) can be any screening device adapted to separate the polymer still entrained in the vapor stream of the first screening device (3) from the gas components in the gas stream. Preferably, the second screening device (4) is also configured for gravity separation. Even more preferably, the second screening device (4) is a cyclone separator.

[0071] In another preferred embodiment of the invention, the second screening device (4) is a filter. In one embodiment of the invention, the filter (4) includes a flake separator. In another embodiment of the invention, the filter (4) includes a demister. In an even more preferred embodiment, the filter (4) includes both a flake separator and a demister.

[0072] The second (3) and the second screening device (4) can be used in any combination, i.e., two cyclone separators, two filters, one cyclone separator and a filter, or vice versa. However, most preferably, in the screening assembly of the present invention, the first screening device (3) is a cyclone separator and the second screening device (4) is a filter. This combination ensures the highest separation efficiency. In such an embodiment, the inlet of the filter (4) is preferably connected to the second outlet of the cyclone separator (3) via a pipe for the steam flow (e) for the first screening. Furthermore, in such an embodiment, the steam flow (h) for the second screening is removed from the second screening device (4).

[0073] Furthermore, preferably, the first outlet of the first screening device (3) for removing the condensate phase can be connected to the condensate vapor composition stream (d) via a pipe for screening the condensate vapor composition stream (f). In such an arrangement, the condensate phase of the first screening device (3) is reused, improving energy efficiency and reducing the cost of the entire process.

[0074] Similarly, preferably, the first outlet of the second screening device (4) for removing the condensed phase can be connected to the condensed vapor composition stream (d) via a pipe for screening the condensed vapor composition stream (f).

[0075] Even more preferably, the screening assembly further includes a condensed vapor composition container (5) into which the condensed vapor composition stream (f) is introduced and from which the condensed vapor composition stream (d) is removed. More preferably, a condensed vapor cleaning stream (g) is removed from the condensed vapor composition stream (d). The condensed vapor composition container (5) forms a reservoir for the condensed vapor composition, thereby further ensuring the reliable operability of the screening assembly.

[0076] In a preferred embodiment, the condensed vapor cleaning stream (g) is connected to the separation unit (2) by returning the condensed vapor composition to its boiling point for evaporation in the separation unit (2). The polymer is recovered through the separation unit in this way, avoiding additional work, energy and cost.

[0077] Preferably, the screening assembly includes a first pump (6) for compressing the condensed vapor composition stream (d). Typically, the condensed vapor composition must be compressed again to match the pressure in the lean polymer vapor stream (c) taken from the separation device (2) before the lean polymer vapor stream (c) is injected into the condensed vapor composition stream (d).

[0078] A first preferred embodiment of the screening component (Figure 1)

[0079] Therefore, in summary, the first preferred embodiment of the present invention relates to a screening assembly comprising:

[0080] A flash separator (2) is fluidly connected to the polymerization reactor (1) via a pipe for an effluent stream (a) comprising a mixture of polymer and hydrocarbons, wherein the flash separator (2) is configured to separate the effluent stream (a) into a polymer-rich stream (b) and a polymer-lean vapor stream (c), wherein the flash separator (2) includes an inlet, a first outlet for removing the polymer-rich stream (b), and a second outlet for removing the polymer-lean vapor stream (c).

[0081] A cyclone separator (3) is connected to a second outlet of the flash separator (2) via a pipe for the lean polymer vapor stream (c), wherein the cyclone separator (3) is configured to inject a condensed vapor composition containing a hydrocarbon mixture into the lean polymer vapor stream (c) via a pipe for a condensed vapor composition stream (d), and to screen out a condensed vapor composition stream (f) containing polymer and the condensed vapor composition from the lean polymer vapor stream (c), wherein the cyclone separator (3) includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase.

[0082] A filter (4) comprising an inlet, a first outlet for removing the condensate phase, and a second outlet for removing the vapor phase; wherein the inlet of the filter (4) is connected to the second outlet of the cyclone separator (3) via a pipe for a vapor stream (e) for first screening.

[0083] The first outlet of the cyclone separator (3) for removing the condensate phase is connected to the condensate vapor composition stream (d) via a pipe for screening the condensate vapor composition stream (f).

[0084] The first outlet of the filter (4) for removing the condensate phase is connected to the condensate vapor composition stream (d) via a pipe for screening the condensate vapor composition stream (f).

[0085] The screening assembly further includes a condensed vapor composition container (5), into which the screened condensed vapor composition stream (f) is introduced and the condensed vapor composition stream (d) is removed.

[0086] The condensed steam cleaning stream (g) is taken from the condensed steam composition stream (d) and fed into the separation device (2).

[0087] The screening assembly includes a first pump (6) for compressing the condensed vapor composition stream (d).

[0088] Preferably, the effluent is removed from the polymerization reactor (1), and more preferably from the solution polymerization reactor.

[0089] Preferably, the screening assembly of the present invention further includes a condenser (7) having an inlet and an outlet, wherein the inlet of the condenser (7) is connected to a second outlet of the first screening device (3) and / or a second outlet of the second screening device (4). In such an embodiment, the first and second screening vapor streams can be converted back into condensed form. This condensation is necessary if these gas streams are again used to provide the condensed form for applications such as spraying.

[0090] Furthermore, preferably, the outlet of the condenser (7) is connected to the inlet of the second (3) and / or the second screening device (4) via a pipe for a vapor stream (j) used for spray condensation, and wherein the first screening device (3) and / or the second screening device (4) are configured to spray the vapor stream (j) used for spray condensation into the lean polymer vapor stream (c). In this arrangement, the condensate phase of the first screening device (3) and / or the second screening device (4) can be reused, thereby improving energy efficiency and reducing the overall cost of the process. Another advantage is that the polymer concentration can be controlled by feeding the vapor stream (j) used for spray condensation and the condensation steam cleaning stream (g) to prevent excessive polymer content.

[0091] Preferably, the screening assembly further includes a filtered condensed vapor stream container (8), into which the filtered condensed vapor stream (i) connected to the outlet of the condenser (7) is introduced and the spray-condensed vapor stream (j) is removed. Furthermore, the filtered condensed vapor stream container (8) forms a reservoir for the filtered condensed vapor stream, which further ensures the reliable operability of the screening assembly.

[0092] Preferably, the filtered condensed steam cleaning stream (k) is taken out from the filtered condensed steam stream container (8).

[0093] Preferably, the sieving assembly of the present invention further includes a second pump (9) for compressing the vapor stream (j) for spray condensation. This condensation is necessary if these gas streams are used again to provide a condensed form of the application, such as a spray.

[0094] A second preferred embodiment of the screening component (Figure 2)

[0095] Therefore, in summary, the second preferred embodiment of the present invention, as shown in FIG2, relates to a screening assembly comprising:

[0096] A separation device (2) is fluidly connected to the polymerization reactor (1) via a pipe for an effluent stream (a), the effluent stream (a) comprising a mixture of polymer and hydrocarbons, wherein the separation device (2) is configured to separate the effluent stream (a) into a polymer-rich stream (b) and a polymer-lean vapor stream (c), wherein the separation device (2) includes an inlet, a first outlet for removing the polymer-rich stream (b), and a second outlet for removing the polymer-lean vapor stream (c).

[0097] A first screening device (3) is connected to a second outlet of a separation device (2) via a pipe for a lean polymer vapor stream (c). The first screening device (3) is configured to inject a condensed vapor composition containing a hydrocarbon mixture into the lean polymer vapor stream (c) via a pipe for a condensed vapor composition stream (d), and to screen out a condensed vapor composition stream (f) containing a polymer and the condensed vapor composition from the lean polymer vapor stream (c). The first screening device (3) includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase.

[0098] The first outlet of the first screening device (3) for removing the condensed phase is connected to the condensed vapor composition stream (d) via a pipe for screening the condensed vapor composition stream (f).

[0099] The screening assembly further includes a condensed vapor composition container (5), into which the screened condensed vapor composition stream (f) is introduced and the condensed vapor composition stream (d) is removed.

[0100] The condensed steam cleaning stream (g) is taken from the condensed steam composition stream (d) and fed into the separation device (2).

[0101] The screening assembly also includes a first pump (6) for compressing the condensed vapor composition stream (d).

[0102] The screening assembly further includes a condenser (7) having an inlet and an outlet, wherein the inlet of the condenser (7) is connected to a second outlet of the first screening device (3).

[0103] The screening assembly also includes a container (8) for filtered condensed vapor streams, into which the filtered condensed vapor stream (i) connected to the outlet of the condenser (7) is introduced, and from which spray-condensed vapor streams (j) are removed.

[0104] The outlet of the condenser (7) is connected to the inlet of the first screening device (3) via a pipe for a vapor stream (j) for spray condensation, and the first screening device (3) is configured to spray the vapor stream (j) for spray condensation into a lean polymer vapor stream (c).

[0105] The screening assembly also includes a second pump (9) for compressing the vapor stream (j) of the spray condensation.

[0106] Preferably, the effluent is removed from the polymerization reactor (1), and more preferably from the solution polymerization reactor.

[0107] A third preferred embodiment of the screening component (Figure 3)

[0108] The third preferred embodiment represents an arrangement of cyclone separators and filters in the order represented by the first preferred embodiment, and a device for reusing the sieved steam stream from the cyclone separators and filters.

[0109] Therefore, in summary, the third preferred embodiment of the present invention relates to a screening assembly comprising:

[0110] A flash separator (2) is fluidly connected to a conduit for an effluent stream (a), the effluent stream (a) comprising a mixture of polymer and hydrocarbons, wherein the flash separator (2) is configured to separate the effluent stream (a) into a polymer-rich stream (b) and a polymer-lean vapor stream (c), wherein the flash separator (2) includes an inlet, a first outlet for removing the polymer-rich stream (b), and a second outlet for removing the polymer-lean vapor stream (c).

[0111] A cyclone separator (3) is connected via a pipe to the second outlet of a flash separator (2), wherein the cyclone separator (3) is configured to inject a condensed vapor composition containing a hydrocarbon mixture into the lean polymer vapor stream (c) via a pipe for a condensed vapor composition stream (d), and to screen out a condensed vapor composition stream (f) containing polymer and the condensed vapor composition from the lean polymer vapor stream (c), wherein the cyclone separator (3) includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase.

[0112] A filter (4) comprising an inlet, a first outlet for removing the condensate phase, and a second outlet for removing the vapor phase; wherein the inlet of the filter (4) is connected to the second outlet of the cyclone separator (3) via a pipe for a vapor stream (e) for first screening.

[0113] The first outlet of the cyclone separator (3) for removing the condensate phase is connected to the condensate vapor composition stream (d) via a pipe for screening the condensate vapor composition stream (f).

[0114] The first outlet of the filter (4) for removing the condensate phase is connected to the condensate vapor composition stream (d) via a pipe for screening the condensate vapor composition stream (f).

[0115] The screening assembly also includes a condensed vapor composition container (5), into which the screened condensed vapor composition stream (f) is introduced and which the condensed vapor composition stream (d) is removed.

[0116] The condensed steam cleaning stream (g) is taken from the condensed steam composition stream (d) and fed into the separation unit (2).

[0117] The screening assembly includes a first pump (6) for compressing the condensed vapor composition stream (d).

[0118] The screening assembly further includes a condenser (7) having an inlet and an outlet, wherein the inlet of the condenser (7) is connected to a second outlet of the cyclone separator (3) and / or a second outlet of the filter (4).

[0119] The screening assembly also includes a container (8) for filtered condensed vapor streams, into which the filtered condensed vapor stream (i) connected to the outlet of the condenser (7) is introduced, and from which the spray-condensed vapor stream (j) is removed.

[0120] The outlet of the condenser (7) is connected via a pipe to the inlet of the cyclone separator (3) and / or the inlet of the filter (4) for a vapor stream (j) used for spray condensation, and the cyclone separator (3) and the filter (4) are configured to spray the vapor stream (j) for spray condensation into a lean polymer vapor stream (c).

[0121] The screening assembly also includes a container (8) for filtered condensed vapor streams, into which the filtered condensed vapor stream (i) connected to the outlet of the condenser (7) is introduced, and where the spray-condensed vapor stream (j) is removed.

[0122] The screening assembly also includes a second pump (9) for compressing the vapor stream (j) of the spray condensation.

[0123] Preferably, the effluent is removed from the polymerization reactor (1), and more preferably from the solution polymerization reactor.

[0124] According to the method of the present invention

[0125] The method of the present invention relates to separating the polymer from an effluent stream (a) comprising a mixture of polymer and hydrocarbon, preferably at least one solvent and at least one monomer.

[0126] Aggregation methods

[0127] The effluent stream can be prepared using any method used for polymer production, which requires subsequent separation of volatile compounds from the polymer after production. Preferably, the invention is applicable to supercritical, solution, and advanced solution polymerization methods. More preferably, continuous supercritical, solution, and advanced solution polymerization methods. Most preferably, the production method includes a continuous solution polymerization method.

[0128] The polymer produced in this invention can be any polymer produced using volatile compounds. Preferably, the polymer produced in this invention is an olefin homopolymer or copolymer. More preferably, the monomer of the polymer is selected from α-olefins having 2 to 4 carbon atoms, preferably ethylene, propylene, 1-butene, and most preferably ethylene. Most preferably, the polymer is a polyethylene copolymer or homopolymer.

[0129] When the polymer is a copolymer, the comonomer is preferably different from the α-olefin monomer and is selected from linear and cyclic olefins and α-olefins having 2 to 12 carbon atoms and mixtures thereof. More preferably, the comonomer is an α-olefin different from the olefin monomer and is selected from linear olefins having 2 to 12 carbon atoms and mixtures thereof, preferably 4 to 10 carbon atoms, and most preferably 1-octene.

[0130] In a most preferred embodiment, the polymer is produced by the solution polymerization method disclosed below.

[0131] Polymerization is typically carried out in the presence of an olefin polymerization catalyst. This catalyst can be any catalyst known in the art capable of polymerizing monomers and optionally comonomers. Therefore, the polymerization catalyst can be the Ziegler-Natta catalyst disclosed in EP-A-280352, EP-A-280353, and EP-A-286148, or the metallocene catalyst disclosed in WO-A-1993025590, US-A-5001205, WO-A-1987003604, and US-A-5001244, or a combination thereof. Other suitable catalysts, such as post-transition metal catalysts, can also be used.

[0132] In solution polymerization, a solvent is also present. The solvent is in a liquid or supercritical state under polymerization conditions. The solvent is typically and preferably a hydrocarbon solvent. The liquid hydrocarbon solvent used is preferably C444. 5-12 Hydrocarbons, which may be unsubstituted or C-substituted. 1-4 Alkyl-substituted, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, and hydrogenated naphtha. More preferably, unsubstituted C4 is used. 6-10 Hydrocarbon solvent.

[0133] Other components may also be added to the reactor. It is known to introduce hydrogen into the reactor to control the molecular weight of the polymer formed during polymerization. The use of different antifouling compounds is also known in the art. Furthermore, different types of activators or retarders can be used to control the activity of the catalyst.

[0134] Typically, the polymer content in the effluent stream, which includes solvent, polymer, unreacted monomer, and optionally comonomer, is 10% to 35% by weight, preferably 12.5% ​​to 30% by weight, and more preferably 15% to 25% by weight.

[0135] The effluent stream is the feed stream to the separation unit. As mentioned above, it can be the product stream from the polymerization reactor. The reaction mixture stream then typically has the polymer content, composition temperature, and pressure described above.

[0136] The effluent stream comprises a polymer, at least one unreacted monomer, and optionally at least one unreacted comonomer. Depending on the polymerization method, the reaction mixture may further comprise at least one solvent.

[0137] Screening methods

[0138] In the most general embodiment of the present invention, a method for sieving polymer from a polymer-lean vapor stream (a) is provided, wherein the method includes the following steps:

[0139] A) Separating the effluent stream (a) containing the polymer and the first hydrocarbon mixture into a polymer-rich stream (b) and a polymer-lean vapor stream (c);

[0140] B) Injecting a stream of condensed vapor composition (d) containing a condensed vapor composition of a hydrocarbon mixture into the lean polymer vapor stream (c);

[0141] C) Sieve the lean polymer vapor stream (c) to obtain a sieved condensed vapor composition stream (f) containing the polymer and the condensed vapor composition.

[0142] Preferably, the effluent stream (a) is removed from the polymerization reaction step. Preferably, the hydrocarbon mixture comprises a solvent, unreacted monomers, and / or comonomers.

[0143] Preferably, the lean polymer vapor stream generated in step A) is superheated. This is due to the conditions typically used in such separation steps. Preferably, step A) is carried out under conditions that allow volatile compounds in the effluent stream to evaporate from a condensate phase primarily comprising the polymer. Preferably, the temperature used in step A) is between 100°C and 400°C, more preferably between 130°C and 300°C, and even more preferably between 170°C and 250°C. Furthermore, the pressure drop associated with the pressure in the effluent stream (a) is preferably greater than 30 barg, more preferably greater than 60 barg, and most preferably greater than 90 barg. Thus, the conditions found in the lean polymer vapor stream (c) are set as a mixture of hydrocarbons, i.e., solvent, unreacted monomers and / or comonomers, not at their condensation point. Therefore, the mixture of compounds typically found in the lean polymer vapor stream (c) is present in gaseous form.

[0144] It has now been surprisingly discovered that injecting a condensed vapor composition containing a hydrocarbon mixture into a polymer-lean vapor stream (c) can significantly reduce polymer entrainment.

[0145] Therefore, step A) is preferably performed using a flash separator.

[0146] Preferably, the polymer in the effluent stream is molten. This ensures optimal mass exchange of volatile compounds evaporated from the polymer in step A).

[0147] Preferably, step C) comprises gravity separation of the condensed vapor composition stream (f) from the lean polymer stream (c). Gravity separation can be performed using any gravity separation method known in the art and suitable for polymer separation. However, cyclone separators and filters are most preferred. Therefore, more preferably, step C) is performed using a cyclone separator (3). Similarly, in a parallel, more preferred embodiment, step C) is performed using a filter (4).

[0148] Step C) can also be performed using a combination of cyclone separators (3) and filters (4), i.e., two cyclone separators, two filters, one cyclone separator and one filter, or vice versa. However, most preferably, step C) is performed using cyclone separators (3) followed by filters (4). This combination ensures the highest separation efficiency.

[0149] In step C), where the cyclone separator (3) and filter (4) are used in this order, preferably, the vapor phase of the cyclone separator (3) is introduced into the filter (4) through the vapor stream (e) of the first sieve.

[0150] Preferably, in step C), the filter (4) includes a flake separator and / or a demister. More preferably, in step C), the filter (4) includes a flake separator and a demister.

[0151] In a preferred embodiment of the invention, in step C), the sieved condensed vapor composition stream (f) is reintroduced into step B) via the condensed vapor composition stream (d). In this arrangement, the condensate phase from step (c), for example from the cyclone separator (3) and / or filter (4), is reused, thereby improving energy efficiency and reducing the overall cost of the process.

[0152] Furthermore, preferably, in step C), the sieved condensed vapor composition stream (f) is introduced into the condensed vapor composition container (5), and the condensed vapor composition stream (d) is removed from the condensed vapor composition container (5). The condensed vapor composition container (5) forms a reservoir for the condensed vapor composition, which further ensures the reliable operability of the sieving assembly. More preferably, in step C), the condensed vapor composition wash stream (g) is removed from the condensed vapor composition stream (d). In a preferred embodiment, the condensed vapor wash stream (g) is at least partially reintroduced into step A) by allowing the condensed vapor composition to return to its boiling point for evaporation in the separation device (2). The polymer is recovered in this way through the separation device, avoiding additional work, energy, and costs.

[0153] Furthermore, more preferably, in step C), the first pump (6) is used to compress the condensed vapor composition stream (d).

[0154] A first preferred embodiment of the screening method (Figure 1)

[0155] Therefore, in summary, the first preferred embodiment of the present invention relates to a method for sieving polymers from a polymer-lean vapor stream, wherein the method includes the following steps:

[0156] A) Separating the effluent stream (a) containing the polymer and the first hydrocarbon mixture into a polymer-rich stream (b) and a polymer-lean vapor stream (c);

[0157] B) Injecting a stream of condensed vapor composition (d) containing a condensed vapor composition of a second hydrocarbon mixture into the lean polymer vapor stream (c);

[0158] C) Sieve the lean polymer vapor stream (c) to obtain a sieved condensed vapor composition stream (f) containing the polymer and the condensed vapor composition.

[0159] Step A) is performed using a flash separator.

[0160] Step C) is performed in this order using a cyclone separator (3) and a filter (4), wherein the vapor phase of the cyclone separator (3) is introduced into the filter (4) via a first sieved vapor stream (e).

[0161] In step C), the sieved condensed vapor composition stream (f) is reintroduced into step B) via the condensed vapor composition stream (d).

[0162] In step C), the selected condensed vapor composition stream (f) is introduced into the condensed vapor composition container (5), and the condensed vapor composition stream (d) is removed from the condensed vapor composition container (5).

[0163] In step C), the condensed vapor composition cleaning stream (g) is removed from the condensed vapor composition stream (d) and at least partially reintroduced into step A), and

[0164] In step C), the first pump (6) is used to compress the condensed vapor composition stream (d).

[0165] Preferably, the effluent stream (a) is removed from the polymerization reaction step.

[0166] Preferably, in step C), the vapor stream (e) from the first sieve taken from the first sieve device (3) and / or the vapor stream (h) from the second sieve taken from the second sieve device (4) are condensed by the condenser (7) to generate a filtered condensed vapor stream (i), which is then reintroduced into step B by a vapor stream (j) condensed by a spray jet.

[0167] Preferably, in step C), the filtered condensed vapor stream (i) is introduced into the filtered condensed vapor stream container (8) and the spray condensed vapor stream (j) is removed from the filtered condensed vapor stream container (8).

[0168] Preferably, in step C), the filtered condensed steam cleaning stream (k) is taken out from the filtered condensed steam stream container (8).

[0169] Preferably, in step C), a second pump (9) is used to compress the vapor stream (j) from the spray condensation. A second preferred embodiment of the sieving method (Figure 2).

[0170] Therefore, in summary, the second preferred embodiment of the present invention, as shown in FIG2, relates to a method for sieving polymers from a polymer-lean vapor stream, wherein the method includes the following steps:

[0171] A) Separating the effluent stream (a) containing the polymer and the first hydrocarbon mixture into a polymer-rich stream (b) and a polymer-lean vapor stream (c);

[0172] B) Injecting a stream of condensed vapor composition (d) containing a condensed vapor composition of a second hydrocarbon mixture into the lean polymer vapor stream (c);

[0173] C) Sieve the lean polymer vapor stream (c) to obtain a sieved condensed vapor composition stream (f) containing the polymer and the condensed vapor composition.

[0174] Step A) is performed using a flash separator.

[0175] In step C), the sieved condensed vapor composition stream (f) is reintroduced into step B) via the condensed vapor composition stream (d).

[0176] In step C), the sieved condensed vapor composition stream (f) is introduced into the condensed vapor composition container (5), and the condensed vapor composition stream (d) is removed from the condensed vapor composition container (5).

[0177] In step C), the condensed vapor composition cleaning stream (g) is removed from the condensed vapor composition stream (d) and the condensed vapor composition cleaning stream (g) is at least partially reintroduced into step A), and

[0178] In step C), the first pump (6) is used to compress the condensed vapor composition stream (d).

[0179] In step C), the first sieved vapor stream (e) is condensed by the condenser (7) to produce a filtered condensed vapor stream (i), which is then reintroduced into step B) via a spray-condensed vapor stream (j).

[0180] In step C), the filtered condensed vapor stream (i) is introduced into the filtered condensed vapor stream container (8) and the spray-condensed vapor stream (j) is removed from the filtered condensed vapor stream container (8).

[0181] In step C), the filtered condensed steam cleaning stream (k) is taken out from the filtered condensed steam stream container (8).

[0182] In step C), the second pump (9) is used to compress the vapor stream (j) of the spray condensation.

[0183] Preferably, the effluent stream (a) is removed from the polymerization reaction step.

[0184] A third preferred embodiment of the screening method (Figure 3)

[0185] The third preferred embodiment represents a combination of methods including step C), wherein step C) uses a cyclone separator and filter in the order represented by the first preferred embodiment, and an additional step in step C) is used to reuse the sieved steam stream from the cyclone separator and filter.

[0186] Therefore, in summary, the third preferred embodiment of the present invention, as shown in FIG3, relates to a method for sieving polymers from a polymer-lean vapor stream, wherein the method includes the following steps:

[0187] A) Separating the effluent stream (a) containing the polymer and the first hydrocarbon mixture into a polymer-rich stream (b) and a polymer-lean vapor stream (c);

[0188] B) Injecting a stream of condensed vapor composition (d) containing a condensed vapor composition of a second hydrocarbon mixture into the lean polymer vapor stream (c);

[0189] C) Sieve the lean polymer vapor stream (c) to obtain a sieved condensed vapor composition stream (f) containing the polymer and the condensed vapor composition.

[0190] Step A) is performed using a flash separator.

[0191] Step C) is performed in this order using a cyclone separator (3) and a filter (4), wherein the vapor phase of the cyclone separator (3) is introduced into the filter (4) via a first sieved vapor stream (e).

[0192] In step C), the sieved condensed vapor composition stream (f) is reintroduced into step B) via the condensed vapor composition stream (d).

[0193] In step C), the sieved condensed vapor composition stream (f) is introduced into the condensed vapor composition container (5), and the condensed vapor composition stream (d) is removed from the condensed vapor composition container (5).

[0194] In step C), the condensed vapor composition cleaning stream (g) is removed from the condensed vapor composition stream (d) and at least partially reintroduced into step A), and

[0195] In step C), the first pump (6) is used to compress the condensed vapor composition stream (d).

[0196] In step C), the vapor stream (e) from the first sieve taken from the first sieve device (3) and / or the vapor stream (h) from the second sieve taken from the second sieve device (4) are condensed by the condenser (7) to generate a filtered condensed vapor stream (i), which is then reintroduced into step B) by the vapor stream (j) condensed by the jet spray.

[0197] In step C), the filtered condensed vapor stream (i) is introduced into the filtered condensed vapor stream container (8) and the spray condensed vapor stream (j) is removed from the filtered condensed vapor stream container (8).

[0198] In step C), the filtered condensed steam cleaning stream (k) is taken out from the filtered condensed steam stream container (8).

[0199] In step C), the second pump (9) is used to compress the vapor stream (j) of the spray condensation.

[0200] Preferably, the effluent stream (a) is removed from the polymerization reaction step.

[0201] Application of the screening component of the present invention

[0202] The present invention also relates to the use of the screening assembly according to the invention for preventing scaling in a polymerization process.

Claims

1. A method for sieving polymer from a polymer-lean vapor stream, wherein the method comprises the following steps: A) Separating the effluent stream (a) containing the polymer and the first hydrocarbon mixture into a polymer-rich stream (b) and a polymer-lean vapor stream (c); B) Injecting a stream of condensed vapor composition (d) containing a condensed vapor composition of a second hydrocarbon mixture into the lean polymer vapor stream (c); C) Sieve the lean polymer vapor stream (c) to obtain a sieved condensed vapor composition stream (f) containing the polymer and the condensed vapor composition. Step A is performed using a flash separator (2).

2. The method according to claim 1, wherein step C) is performed in that order using a cyclone separator (3) and a filter (4), wherein the vapor phase of the cyclone separator (3) is introduced into the filter (4) via a first sieved vapor stream (e), and wherein a second sieved vapor stream (h) is removed from the filter (4).

3. The method according to claim 1 or 2, wherein in step C), the sieved condensed vapor composition stream (f) is reintroduced into step B) via the condensed vapor composition stream (d), and wherein in step C), the sieved condensed vapor composition stream (f) is introduced into the condensed vapor composition container (5) and the condensed vapor composition stream (d) is removed from the condensed vapor composition container (5).

4. The method according to claim 2, wherein in step C), the first sieved vapor stream (e) and / or the second sieved vapor stream (h) are condensed by a condenser (7) to produce a filtered condensed vapor stream (i), which is then reintroduced into step B by a vapor stream (j) condensed by a jet spray.

5. The method according to claim 4, wherein in step C), the filtered condensed vapor stream (i) is introduced into the filtered condensed vapor stream container (8) and the spray condensed vapor stream (j) is removed from the filtered condensed vapor stream container (8).

6. A screening assembly comprising: - A separation device (2), fluidly connected to a conduit for an effluent stream (a), the effluent stream (a) comprising a polymer and a first hydrocarbon mixture, wherein the separation device (2) is configured to separate the effluent stream (a) into a polymer-rich stream (b) and a polymer-lean vapor stream (c), wherein the separation device (2) includes an inlet, a first outlet for removing the polymer-rich stream (b), and a second outlet for removing the polymer-lean vapor stream (c). - A first screening device (3) is connected to a second outlet of the separation device (2) via a pipe for the lean polymer vapor stream (c), wherein the first screening device (3) is configured to inject a condensed vapor composition containing a second hydrocarbon mixture into the lean polymer vapor stream (c) via a pipe for a condensed vapor composition stream (d), and to screen a condensed vapor composition stream (f) containing the polymer and the condensed vapor composition from the lean polymer vapor stream (c), wherein the first screening device (3) includes an inlet, a first outlet for removing the condensed phase, and a second outlet for removing the vapor phase. The separation device (2) is a flash separator.

7. The screening component according to claim 6, wherein, The screening assembly further includes a second screening device (4), which includes an inlet, a first outlet for removing the condensate phase, and a second outlet for removing the vapor phase.

8. The screening assembly according to claim 7, wherein the first screening device (3) is a cyclone separator and the second screening device (4) is a filter and wherein the filter (4) is connected to the cyclone separator (3) via a pipe for the steam flow (e) for the first screening.

9. The screening assembly according to any one of claims 6 to 8, wherein the first outlet of the first screening device (3) for removing the condensed phase is connected to the condensed vapor composition stream (d) via a pipe for screening the condensed vapor composition stream (f).

10. The screening assembly according to claim 7 or 8, wherein the first outlet of the second screening device (4) for removing the condensed phase is connected to the condensed vapor composition stream (d) via a pipe for the condensed vapor composition stream (f) for the screening.

11. The screening assembly according to claim 9, wherein the screening assembly further comprises a condensed vapor composition container (5), into which the condensed vapor composition stream (f) of the screening is introduced and the condensed vapor composition stream (d) is removed from the container.

12. The screening assembly according to claim 7 or 8, wherein the screening assembly further comprises a condenser (7) having an inlet and an outlet, wherein the inlet of the condenser (7) is connected to a second outlet of the first screening device (3) and / or a second outlet of the second screening device (4), and wherein the outlet of the condenser (7) is connected to the inlet of the first screening device (3) and / or the second screening device (4) via a conduit for a vapor stream (j) for spray condensation, and wherein the first screening device (3) and / or the second screening device (4) are configured to spray the vapor stream (j) for spray condensation into the lean polymer vapor stream (c), and wherein the screening assembly further comprises a filtered condensed vapor stream container (8) into which a filtered condensed vapor stream (i) connected to the outlet of the condenser (7) is introduced and from which the vapor stream (j) for spray condensation is removed.

13. Use of the screening assembly according to any one of claims 6 to 12 for preventing scaling in a polymerization process.

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