EP-4537919-B1 - SCREENING ASSEMBLY AND USE FOR SCREENING POLYMER FROM AN EFFLUENT STREAM AT REDUCED LEVELS OF POLYMER ENTRAINMENT

EP4537919B1EP 4537919 B1EP4537919 B1EP 4537919B1EP-4537919-B1

Inventors

Sleijster, Henry
AL-HAJ ALI, Mohammad
SATTAR, Mubashar
AJELLAL, Noureddine
WEBER, Charlotta

Dates

Publication Date: 20260513
Application Date: 20200813

Claims (5)

A screening polymer-rich assembly comprising - a separating device (2) connected to a conduit for an effluent stream (a) comprising a mixture of hydrocarbons, wherein the separating 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 first separation device (2) comprises an inlet, a first outlet for withdrawing a polymer-rich stream (b), and a second outlet for withdrawing a polymer-lean vapor stream (c), - a screening device (3) connected to the separating device (2) via a conduit for the polymer-lean vapor stream (c), wherein the screening device (3) comprises: - a first inlet (4) connected to the conduit for the polymer-lean vapor stream (c), - a first outlet (5) for withdrawing a cleaned vapor stream (d), - a second outlet (6) for withdrawing a polymer-comprising condensed vapor stream (e), and - at least one second inlet (7, 8) for introducing a condensed vapor stream (f, g) wherein the at least one second inlet (7, 8) comprises - a first second inlet (7) for introducing a first condensed vapor stream (f), and - a second second inlet (8) for introducing a second condensed vapor stream (g), wherein the first second inlet (7) is positioned above the first inlet (4) and below the second second inlet (8) with respect to the height of the screening device (3), and wherein the second second inlet (8) is positioned above the first second inlet (7) and below the first outlet (5) with respect to the height of the screening device (3) and wherein the first inlet (4) is configured for spraying condensed vapor into the polymer-lean vapor stream (c) wherein a polymer-comprising condensed vapor stream (e) connected to the second outlet (6) and a recycle condensed vapor stream (j) connected to the separating device (2) are fluidly connected, preferably fluidly connected via the pump (12) and a heater (13).
The screening assembly according to claim 1, wherein the polymer-comprising condensed vapor stream (e) connected to the second outlet (6) and the condensed vapor stream (f) connected to the first second inlet (7) are fluidly connected, preferably fluidly connected via a pump (12).
The screening assembly according to claim 1 or 2, further comprising a third inlet (9) for introducing a heated condensed vapor stream (h), and wherein the polymer-comprising condensed vapor stream (e) connected to the second outlet (6) and the heated condensed vapor stream (h) connected to the third inlet (9) are fluidly connected, preferably fluidly connected via the pump (12) and the heater (13).
The screening assembly according to any of the preceding claims 1 to 3, further comprising a condenser (14) comprising an inlet and an outlet, wherein the first outlet (5) is fluidly connected to the inlet of the condenser (14) via a conduit for the cleaned vapor stream (d), wherein the outlet of the condenser (14) is fluidly connected to the second second inlet (8) via a conduit for the second condensed vapor stream (g).
Use of a screening assembly according to any of the preceding claims 1 to 4 for preventing fouling.

Description

The present invention is concerned with a screening assembly for screening polymer from an effluent stream. In particular, the screening assembly can be used in solution polymerization processes. Background Typically, in solution polymerization processes, reactors are operated with relatively low polymer concentrations in the reactor, whereby low polymer concentrations typically are considered to be lower than 30 wt% with respect to the total amount of polymer, solvent(s), monomers, and optional comonomers used. Furthermore, reactors in solution polymerization processes are typically operated at reactor temperatures higher than in gas phase polymerization processes. The advantage of higher temperatures are higher catalyst activities and, hence, better catalytic efficiency. However, the drawbacks are that in cases where the exothermic reaction is fast, too much heat is absorbed in the reaction mixture leading to the risk of uncontrolled reactions. To control such fast exothermic reactions and uncontrolled reactions, polymer concentrations are typically within 15 to 25 wt% leading to controlled exothermic heat production. Therefore, as a result, the effluent stream comprises respective amounts of undesired hydrocarbons, such as solvent, unreacted monomers and optionally comonomers, which have to be removed from the polymer in process steps subsequently to the polymerization reaction step. While solution polymerization processes known in the art vary in these subsequent process steps, nearly all of them typically make use of the following steps: a) heating the polymer melt solution under pressure and b) depressurizing the solution to let volatile compounds evaporate. Typically, such solution polymerization processes are carried out under conditions, where the reactor pressures are higher than 50 barg and the temperature at the reactor outlet is higher than 150°C. In some of the solution polymerization technologies known from the prior art, in the subsequent step, the solution stream is heated up to above 200 °C followed by a pressure drop down to vacuum levels to produce the final polymer. Typically, such separation is carried out in a fashion that a condensed stream and a vapor stream are formed, i.e. in a flash separator. In a typical reactor assembly or process, such vapor stream from said evaporation step is condensed and fed to recovery sections. For example, it can be reused as solvent and/or as a source for unreacted monomer and/or comonomer. In certain applications of polymer, particularly low levels of volatiles in the polymer are needed, whereby volatiles can be inter alia represented by hydrocarbons, such as solvent molecules and/or unreacted monomers or comonomers still left in the produced polymer. To achieve such low volatile levels in the polymer, multi-step evaporation processes have been developed. In particular, it is known from the art that two- or three-step evaporation processes are at least needed to reach an acceptable low level of volatiles for certain market applications of the polymer in most cases with the help of additional equipment like a devolitization extruder or kneader as a last step. Typically, also in each step of the multi-step processes, the vapor streams are subsequently condensed and may be reused as reactor feed of the process or feed to recovery sections, where hydrocarbons, such as solvent, comonomer and monomer, are separated beforehand. Patent application US2008214745A1 discloses a process for the polymerisation of olefins wherein at least part of a stream, preferably a catalytically active stream, withdrawn from a polymerisation reactor is passed through a fractionator so as to remove hydrogen and active fines. Patent application US2012264911A1 discloses a method of treating a polymerization reactor effluent stream comprising recovering the reactor effluent stream from the polymerization reactor, flashing the reactor effluent stream to form a flash gas stream, separating the flash gas stream into a first top stream, a first bottom stream, and a side stream, wherein the side stream substantially comprises hexane, separating the first top stream into a second top stream and a second bottom stream, wherein the second bottom stream substantially comprises isobutene, and separating the second top stream into a third top stream and a third bottom stream; wherein the third top stream substantially comprises ethylene, and wherein the third bottom stream is substantially free of olefins. Patent application WO2019162445A1 discloses .a process for separating hydrogen from a gaseous feed stream in a polymerisation process, comprising the steps i) polymerising an olefin monomer and optionally at least one olefin comonomer in the presence of a solvent, optionally in the presence of hydrogen, so as to form a polymerisation reaction mixture comprising a polyolefin polymer, unreacted monomer(s), solvent and hydrogen; (ii) separating said polyolefin polymer from said unreacted monom