Patent Description:
In many systems and methods for volatile component removal, a purge column is utilized, but often the polymer solids temperature entering the purge column is unacceptably low, resulting in poor volatile removal, long residence times, and large column sizes in order to meet a desired final volatile content of, for example, less than <NUM> wt% (<NUM> ppmw (ppm by weight)) of volatile components. Thus, the present invention is generally directed to systems and methods for significantly increasing the temperature of the polymer solids entering the purge column. <CIT> relates to a method for transferring polymer within a polymerization system, including continuously withdrawing the polymer from the reactor and conveying the polymer from a reactor to a flash chamber via a pressure differential between the reactor and the flash chamber.

According to one aspect of the invention, there is provided a method for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor. The method includes: (i) reducing a pressure of the effluent stream to remove a first portion of the volatile components from polymer solids, the polymer solids having a solids temperature from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor; (ii) fluidizing the polymer solids and heating the polymer solids to a solids temperature from at least <NUM> (<NUM> °F) above the solids temperature in step (i) and up to <NUM> (<NUM> °F) greater than the reaction temperature, and wherein a second portion of the volatile components are removed; and (iii) contacting the polymer solids with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm by weight (ppmw)) of volatile components.

According to another aspect of the invention, there is provided a polyethylene recovery and volatile removal system. The system includes: (a) a flash chamber for reducing a pressure of an ethylene polymer effluent stream from an ethylene polymerization reactor and for removing a first portion of volatile components from polymer solids, wherein the flash chamber is configured to form the polymer solids at a solids temperature from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor; (b) a fluidized bed heater for fluidizing the polymer solids and for heating the polymer solids to a solids temperature from at least <NUM> (<NUM> °F) above the solids temperature in (a) and up to <NUM> (<NUM> °F) greater than the reaction temperature, wherein the fluidized bed heater is configured to remove a second portion of the volatile components; and (c) a purge column for contacting the polymer solids with a stripping gas, wherein the purge column is configured to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppmw (ppm by weight)) of volatile components.

Polyethylene recovery and volatile removal systems are described herein. One such system can comprise (a) a flash chamber for reducing the pressure of an ethylene polymer effluent stream from an ethylene polymerization reactor and for removing a first portion of volatile components from polymer solids, wherein the flash chamber is configured to form the polymer solids at a solids temperature from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor, (b) a fluidized bed heater for fluidizing the polymer solids and for heating the polymer solids to a solids temperature from at least about <NUM> (<NUM> °F) above the solids temperature in (a) and up to about <NUM> (<NUM> °F) greater than the reaction temperature, wherein the fluidized bed heater is configured to remove a second portion of the volatile components, and (c) a purge column for contacting the polymer solids with a stripping gas, wherein the purge column is configured to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppmw (ppm by weight)) of volatile components.

Another polyethylene recovery and volatile removal system can comprise (A) a heated fluidized bed flash chamber for heating and for reducing the pressure of an ethylene polymer effluent stream from an ethylene polymerization reactor, and for removing an initial portion of volatile components from polymer solids, wherein the heated fluidized bed flash chamber is configured to form the polymer solids at a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature in the ethylene polymerization reactor, and (B) a purge column for contacting the polymer solids with a stripping gas, wherein the purge column is configured to remove a final portion of the volatile components to produce a polymer solids stream containing less than <NUM> wt% (<NUM> ppmw) of volatile components.

Methods for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor also are provided herein. One such method can comprise (i) reducing the pressure of the effluent stream to remove a first portion of the volatile components from polymer solids, the polymer solids having a solids temperature from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor, (ii) fluidizing the polymer solids while heating to increase the solids temperature from at least about <NUM> (<NUM> °F) above the solids temperature in step (i) and up to about <NUM> (<NUM> °F) greater than the reaction temperature, and wherein a second portion of the volatile components are removed, and (iii) contacting the polymer solids with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm by weight) of volatile components.

Disclosed is a method for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor, in which the method can comprise (I) contacting the effluent stream with a fluidizing gas at a reduced pressure while heating to remove an initial portion of the volatile components from polymer solids, the polymer solids having a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature in the ethylene polymerization reactor, and (II) contacting the polymer solids with a stripping gas to remove a final portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm by weight) of volatile components.

The following figures form part of the present specification and are included. The disclosure may be better understood by reference to one or more of these figures in combination with the detailed description and examples.

To define more clearly the terms used herein, the following definitions are provided. Unless otherwise indicated, the following definitions are applicable to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition from the <NPL>), can be applied, as long as that definition does not conflict with any other disclosure or definition applied herein, or render indefinite or non-enabled any claim to which that definition is applied.

Generally, groups of elements are indicated using the numbering scheme indicated in the version of the periodic table of elements published in <NPL>. In some instances, a group of elements can be indicated using a common name assigned to the group; for example, alkali metals for Group <NUM> elements, alkaline earth metals for Group <NUM> elements, transition metals for Group <NUM>-<NUM> elements, and halogens or halides for Group <NUM> elements.

The term "hydrocarbon" whenever used in this specification and claims refers to a compound containing only carbon and hydrogen, whether saturated or unsaturated. Other identifiers can be utilized to indicate the presence of particular groups in the hydrocarbon (e.g., halogenated hydrocarbon indicates the presence of one or more halogen atoms replacing an equivalent number of hydrogen atoms in the hydrocarbon). The term "hydrocarbyl group" is used herein in accordance with the definition specified by IUPAC: a univalent group formed by removing a hydrogen atom from a hydrocarbon (that is, a group containing only carbon and hydrogen). Non-limiting examples of hydrocarbyl groups include alkyl, alkenyl, aryl, and aralkyl groups, amongst other groups.

For any particular compound or group disclosed herein, any name or structure (general or specific) presented is intended to encompass all conformational isomers, regioisomers, stereoisomers, and mixtures thereof that can arise from a particular set of substituents, unless otherwise specified. The name or structure (general or specific) also encompasses all enantiomers, diastereomers, and other optical isomers (if there are any) whether in enantiomeric or racemic forms, as well as mixtures of stereoisomers, as would be recognized by a skilled artisan, unless otherwise specified. For instance, a general reference to pentane includes n-pentane, <NUM>-methylbutane, and <NUM>,<NUM>-dimethylpropane; and a general reference to a butyl group includes a n-butyl group, a sec-butyl group, an iso-butyl group, and a t-butyl group.

Unless otherwise specified, the term "substituted" when used to describe a group, for example, when referring to a substituted analog of a particular group, is intended to describe any non-hydrogen moiety that formally replaces a hydrogen in that group, and is intended to be non-limiting. Also, unless otherwise specified, a group or groups can also be referred to herein as "unsubstituted" or by equivalent terms such as "non-substituted," which refers to the original group in which a non-hydrogen moiety does not replace a hydrogen within that group. Moreover, unless otherwise specified, "substituted" is intended to be non-limiting and include inorganic substituents or organic substituents as understood by one of ordinary skill in the art.

The terms "contacting," "combining," and the like are used herein to describe systems and methods in which the materials are contacted or combined together in any order, in any manner, and for any length of time, unless otherwise specified. For example, the materials can be contacted or combined by blending, mixing, fluidizing, and the like, using any suitable technique.

The term "polymer" is used herein generically to include olefin homopolymers, copolymers, terpolymers, and the like, as well as alloys and blends thereof. The term "polymer" also includes impact, block, graft, random, and alternating copolymers. A copolymer can be derived from an olefin monomer and one olefin comonomer, while a terpolymer can be derived from an olefin monomer and two olefin comonomers. Accordingly, "polymer" encompasses copolymers and terpolymers. Similarly, the scope of the term "polymerization" includes homopolymerization, copolymerization, and terpolymerization. Therefore, an ethylene polymer would include ethylene homopolymers, ethylene copolymers (e.g., ethylene/α-olefin copolymers), ethylene terpolymers, and the like, as well as blends or mixtures thereof. Thus, an ethylene polymer encompasses polymers often referred to in the art as LLDPE (linear low density polyethylene) and HDPE (high density polyethylene), as well as ULDPE, VLDPE, LDLPE, and the like. As an example, an ethylene copolymer can be derived from ethylene and a comonomer, such as propylene, <NUM>-butene, <NUM>-hexene, or <NUM>-octene. If the monomer and comonomer were ethylene and <NUM>-hexene, respectively, the resulting polymer can be categorized an as ethylene/<NUM>-hexene copolymer. The term "polymer" also includes all possible geometrical configurations, if present and unless stated otherwise, and such configurations can include isotactic, syndiotactic, and random symmetries. The term "polymer" also is meant to include all molecular weight polymers, and is inclusive of lower molecular weight polymers or oligomers. The intent is for the term "polymer" to encompass oligomers (including dimers and trimers) derived from any olefin monomer disclosed herein (as well from an olefin monomer and one olefin comonomer, an olefin monomer and two olefin comonomers, and so forth).

In this disclosure, while systems and methods are described in terms of "comprising" various components or steps, the systems and methods also can "consist essentially of" or "consist of" the various components or steps, unless stated otherwise.

Several types of ranges are disclosed. When a range of any type is disclosed or claimed, the intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein. For example, the temperature of polymer solids can be in certain ranges. By a disclosure that the temperature of the polymer solids can be from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor, the intent is to recite that the solids temperature can be any temperature in the range and, for example, can be equal to about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, about <NUM> (<NUM> °F) less, or about <NUM> (<NUM> °F) less, than the reaction temperature. Additionally, the temperature can be within any range from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less (for example, from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less), and this also includes any combination of ranges between about <NUM> (<NUM> °F) and about <NUM> (<NUM> °F) less than the reaction temperature. Further, in all instances, where "about" a particular value is disclosed, then that value itself is disclosed. Thus, the disclosure that the temperature of the polymer solids can be from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than the reaction temperature also discloses a solids temperature of <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than the reaction temperature (for example, from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less), and this also includes any combination of ranges between <NUM> (<NUM> °F) and <NUM> (<NUM> °F) less than the reaction temperature. Likewise, all other ranges disclosed herein should be interpreted in a manner similar to this example.

Disclosed herein are polyethylene recovery and volatile removal systems, and methods for removing volatile components from an ethylene polymer effluent stream from a polymerization reactor. In conventional systems and methods, the residence time in the purge column and the amount of stripping gas being used to purge the polymer solids can limit the ability of the column to remove volatile hydrocarbon components sufficiently to meet safe handling or environmental restrictions, particularly as polymer production rates are increased and lower density ethylene polymers are produced. Further, purge column sizes often cannot be increased due to cost or physical space limitations.

Moreover, desorption of volatile components from the polymer solids in the flash chamber causes a reduction in the temperature of the polymer solids. However, higher polymer solids temperatures in the purge column are necessary to increase the diffusion rate of volatile hydrocarbons and to partition or transfer more hydrocarbons into the stripping gas. The velocity or flow rate of the stripping gas should be high enough to remove the hydrocarbons, but the solids temperatures cannot be too high during volatile removal, or the ethylene polymer will soften and plug, agglomerate, or stick to equipment surfaces.

While not wishing to be bound by theory, it is believed that simply heating the stripping gas in the purge column does not provide sufficient energy to significantly increase the temperature of the solids and efficiently remove volatile components; the weight ratio of the stripping gas to the polymer solids is too low and the heat capacity of the stripping gas is generally less than that of the polymer solids.

Advantageously, the disclosed systems and methods overcome the drawbacks noted above, and in particular, result in a significant increase in the polymer solids temperature entering the purge column for efficient stripping of volatile components. It was unexpectedly found that an increase in solids temperature in the purge column can both increase the diffusivity of volatile hydrocarbon components in the solid ethylene polymer and increase the partitioning or transfer of the volatile hydrocarbon components from the polymer solids to the stripping gas. These dual impacts can result in an unexpected <NUM>-fold reduction in volatile content for a ~<NUM> (~<NUM> °F) increase in solids temperature. As an example, at a solids temperature of <NUM> (<NUM> °F) and a <NUM> hour residence time in the purge column, the volatile content leaving the purge column can be <NUM> wt% (<NUM> ppmw), whereas for a solids temperature of <NUM> (<NUM> °F) (under the same purge column operating conditions), the volatile content leaving the purge column can be reduced to less than <NUM> wt% (<NUM> ppmw).

Another benefit of the increase in solids temperature is the ability to significantly reduce the purge column size without sacrificing volatile removal capacity. It is estimated that column sizes can be reduced by <NUM>% to <NUM>-<NUM>%, or more. Likewise, with existing purge columns, the residence time can be reduced significantly without sacrificing volatile removal capacity. It is estimated that <NUM>-fold reductions can be achieved; for example, a <NUM>-hour residence time in the purge column can be reduced to <NUM> hour, or a <NUM>-hour residence time can be reduced to <NUM> minutes. Further benefits can include the use of lower quantities of stripping gas in the purge column, and lower emissions and lower volatile contents of the ethylene polymer solids, among others. The stripping gas can be recovered, recycled, or reused in the disclosed systems and methods.

Also in the disclosed systems and methods, a catalyst deactivating agent can be added to the ethylene polymer effluent stream prior to the flash chamber. This is not required, however, and beneficially, a catalyst deactivating agent is not added prior to the flash chamber. Rather, the catalyst deactivating agent can be introduced advantageously along with the fluidizing gas (in the fluidized bed heater) or with the stripping gas (in the purge column), without detrimental plugging or agglomeration of polymer solids. Alternatively, the catalyst deactivating agent can be injected into the polymer solids stream after the purge column. The catalyst deactivating agent can act on any component (e.g., activator, co-catalyst, transition metal component) of the catalyst composition.

This disclosure is directed to a method for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor. For example, a first method can comprise (i) reducing the pressure of the effluent stream to remove a first portion of the volatile components from polymer solids, the polymer solids having a solids temperature from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor, (ii) fluidizing the polymer solids while heating to increase the solids temperature from at least about <NUM> (<NUM> °F) above the solids temperature in step (i) and up to about <NUM> (<NUM> °F) greater than the reaction temperature, and wherein a second portion of the volatile components are removed, and (iii) contacting the polymer solids with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm) by weight of volatile components. A second method can comprise (I) contacting the effluent stream with a fluidizing gas at a reduced pressure while heating to remove an initial portion of the volatile components from polymer solids, the polymer solids having a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature in the ethylene polymerization reactor, and (II) contacting the polymer solids with a stripping gas to remove a final portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm) by weight of volatile components. Generally, the features of the first and second methods (e.g., the reaction temperature, the solids temperature, the stripping gas, and the amount of volatile components, among others) are independently described herein and these features can be combined in any combination to further describe the disclosed methods for removing volatile components. Moreover, additional process steps can be performed before, during, and/or after the steps of these methods, and can be utilized without limitation and in any combination to further describe the first and second methods for removing volatile components, unless stated otherwise.

Referring now to the first method, in which the ethylene polymer effluent stream from the ethylene polymerization reactor contains polymer solids and volatile components. While not limited thereto, the volatile content of the ethylene polymer effluent stream can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, volatile components (e.g., nitrogen, ethylene, comonomer if used, hydrogen if used, inert hydrocarbon condensing agent, etc.) when the ethylene polymerization reactor is a gas phase reactor. The volatile content is normally much higher when the ethylene polymerization reactor is a loop slurry reactor, and the volatile content of the ethylene polymer effluent stream often can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, of volatile components (e.g., ethylene, comonomer if used, hydrogen if used, hydrocarbon diluent such as isobutane, etc.).

In step (i), when the ethylene polymerization reactor is a gas phase reactor, the pressure can be reduced to about <NUM> to <NUM> kPa (<NUM> to about <NUM> psig), or to about <NUM> to <NUM> kPa (<NUM> to about <NUM> psig), and after the first portion of the volatile components is removed, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components. The resultant polymer solids in step (i) typically can have a solids temperature that is from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), or from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), less than the reaction temperature in the ethylene polymerization reactor, when the ethylene polymerization reactor is a gas phase reactor.

In step (i), when the ethylene polymerization reactor is a loop slurry reactor, the pressure can be reduced to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig), to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig), or to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig), and after the first portion of the volatile components is removed, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components. In step (i), the polymer solids in the flash chamber typically have a solids temperature that is from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than the reaction temperature in the ethylene polymerization reactor. In some instances, the resultant polymer solids from step (i) typically are part of an exit stream in which the pressure is further reduced to about <NUM> kPa (about <NUM> psig), about <NUM> kPa (<NUM> psig), or about <NUM> kPa (about <NUM> psig). The resultant polymer solids after step (i) typically can have a solids temperature that is from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), or from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), less than the reaction temperature in the ethylene polymerization reactor, when the ethylene polymerization reactor is a loop slurry reactor.

The polymer solids from step (i) can be fluidized while heating in step (ii), which can increase the solids temperature to at least about <NUM> (<NUM> °F) above the solids temperature in step (i) and up to about <NUM> (<NUM> °F) greater than the reaction temperature. Further, a second portion of the volatile components is removed in step (ii). While volatile removal is not the primary objective of step (ii), any suitable amount of volatile components can be removed, for example, the polymer solids resulting from step (ii) can contain from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%, less volatile components than the polymer solids resulting from step (i).

Beneficially, step (ii) can be performed in a relatively short period of time. Step (ii) can be conducted for a time period that typically falls within a range of from about <NUM> minute to about <NUM> minutes, from about <NUM> minute to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable fluidizing gas can be used in step (ii). For instance, the polymer solids can be fluidized with a fluidizing gas comprising nitrogen (or other inert gas), ethylene, flash chamber gas, a recycled fraction of the second portion of the volatile components removed in step (ii), and the like, as well as combinations thereof. The flash chamber gas can be a portion of the volatile components removed from the polymer solids in step (i). The temperature of the fluidizing gas is not particularly limited, so long as the gas temperature is sufficient to significantly increase the temperature of the polymer solids. Often, the fluidizing gas temperature ranges from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature.

The fluidizing/heating process in step (ii) can increase the solids temperature from at least about <NUM> (<NUM> °F) above (or from at least about <NUM> (<NUM> °F) above, or from at least about <NUM> (<NUM> °F) above) the solids temperature in step (i), and up to about <NUM> (<NUM> °F) greater (or up to about <NUM> (<NUM> °F) greater, or up to about <NUM> (<NUM> °F) greater) than the reaction temperature. Generally, the maximum solids temperature is limited by the vicat softening temperature and/or by the peak melting temperature of the particular ethylene polymer.

In step (iii), the polymer solids - which were heated in step (ii) - can be contacted with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm) by weight of volatile components. In one example, the third portion of volatile components is removed to form the polymer solids stream containing less than about <NUM> wt% (<NUM> ppmw) of volatile components, while in another example, the polymer solids stream contains less than about <NUM> wt% (<NUM> ppmw) of volatile components, and in yet another example, the polymer solids stream contains less than about <NUM> wt% (<NUM> ppmw) of volatile components.

Step (iii) generally can be performed at relatively low pressures. For instance, step (iii) can be conducted at a pressure in a range from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig), or from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig). Step (iii) typically is conducted for any time period sufficient to reduce the volatile content to a desired amount (e.g., less than <NUM> wt% (<NUM> ppmw), less than <NUM> wt% (<NUM> ppmw), etc.), and due to the much higher solids temperature resulting from step (ii), step (iii) can be conducted for a time period that typically falls within a range of from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable stripping gas can be used in step (iii). For instance, the polymer solids can be contacted with a stripping gas comprising nitrogen (or other inert gas), ethylene, and the like, as well as combinations thereof. The temperature of the stripping gas is not particularly limited, but often contacts the polymer solids at a temperature that is from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature. In some examples, stripping gas at ambient temperature and up to about <NUM> (<NUM> °F) can be used.

Referring now to the second method, in which the ethylene polymer effluent stream from the ethylene polymerization reactor contains polymer solids and volatile components. Similar to the first method, and while not limited thereto, the volatile content of the ethylene polymer effluent stream in the second method can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, volatile components when the ethylene polymerization reactor is a gas phase reactor. The volatile content is normally much higher when the ethylene polymerization reactor is a loop slurry reactor, and the volatile content of the ethylene polymer effluent stream in the second method often can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, of volatile components.

In step (I) of the second method, the effluent stream can be contacted with a fluidizing gas at a reduced pressure while heating to remove an initial portion of the volatile components from the polymer solids, the resultant polymer solids having a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature in the ethylene polymerization reactor. Any suitable pressure can be used in step (I), but generally the pressure is in a range from about <NUM> to <NUM> kPa (about <NUM> about <NUM> psig) in some examples, and from about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig) in other examples.

After the initial portion of the volatile components is removed, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components, when the ethylene polymerization reactor is a gas phase reactor. When the ethylene polymerization reactor is a loop slurry reactor, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components.

The resultant polymer solids in step (I) - after fluidizing and heating at a reduced pressure - can have a significantly increased temperature. Often, the solids temperature can be from about <NUM> (<NUM> °F) less (or from about <NUM> (<NUM> °F) less, or from about <NUM> (<NUM> °F) less) than the reaction temperature in the ethylene polymerization reactor, and up to about <NUM> (<NUM> °F) greater (or up to about <NUM> (<NUM> °F) greater, or up to about <NUM> (<NUM> °F) greater) than the reaction temperature.

Beneficially, step (I) can be performed in a relatively short period of time. Step (I) can be conducted for a time period that typically falls within a range of from about <NUM> minute to about <NUM> minutes, from about <NUM> minute to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable fluidizing gas can be used in step (I). For instance, the polymer solids can be fluidized with a fluidizing gas comprising nitrogen (or other inert gas), ethylene, propylene, butane, isobutane, a recycled fraction of the initial portion of the volatile components removed in step (I), and the like, as well as combinations thereof. The temperature of the fluidizing gas is not particularly limited, so long as the gas temperature is sufficient to significantly increase the temperature of the polymer solids. Often, the fluidizing gas temperature ranges from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature.

Step (II) of the second method can be performed as described above for step (iii) of the first process. Thus, the polymer solids - which are heated in step (I) - can be contacted with a stripping gas to remove a final portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm by weight) of volatile components; alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components; alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components; or alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components. Like step (iii), step (II) generally can be performed at relatively low pressures: for example, from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig), or from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig). Step (II) typically is conducted for any time period sufficient to reduce the volatile content to a desired amount (e.g., less than <NUM> wt% (<NUM> ppmw), less than <NUM> wt% (<NUM> ppmw), etc.), and due to the much higher solids temperature resulting from step (I), step (II) can be conducted for a time period that typically falls within a range of from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable stripping gas can be used in step (II). Therefore, the polymer solids can be contacted with a stripping gas comprising nitrogen (or other inert gas), ethylene, and the like, as well as combinations thereof. The temperature of the stripping gas is not particularly limited, but often contacts the polymer solids at a temperature that is from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature. In some examples, stripping gas at ambient temperature and up to about <NUM> (<NUM> °F) can be used.

Both the first and second methods for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor can further comprise a step of converting the polymer solids stream into solid polymer pellets. This can be accomplished via a pelletizing extruder or other suitable technique. This disclosure is also directed to, and encompasses, the solid polymer pellets produced by any of the methods and polymerization processes disclosed herein.

A catalyst deactivating agent (e.g., water, an alcohol, a natural source oil, a polyethylene glycol, a polypropylene glycol, etc.) can be incorporated into the ethylene polymer effluent stream prior to step (i) or step (I), if desired. While the catalyst deactivating agent can be added at this stage of the process, other options may be more beneficial. For instance, the stripping gas can further include a catalyst deactivating agent (e.g., air), or alternatively, the fluidizing gas can further comprise a catalyst deactivating agent, in both the first and second methods.

In another example, the first and second methods can further comprise a step of introducing a catalyst deactivating agent (e.g., air) into the polymer solids stream after step (iii) or step (II), for instance, before converting into solid polymer pellets via extrusion.

A first polyethylene recovery and volatile removal system can comprise (a) a flash chamber for reducing the pressure of an ethylene polymer effluent stream from an ethylene polymerization reactor and for removing a first portion of volatile components from polymer solids, wherein the flash chamber is configured to form the polymer solids at a solids temperature from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F) less than a reaction temperature of the ethylene polymerization reactor, (b) a fluidized bed heater for fluidizing the polymer solids and for heating the polymer solids to a solids temperature from at least about <NUM> (<NUM> °F) above the solids temperature in (a) and up to about <NUM> (<NUM> °F) greater than the reaction temperature, wherein the fluidized bed heater is configured to remove a second portion of the volatile components, and (c) a purge column for contacting the polymer solids with a stripping gas, wherein the purge column is configured to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppmw (ppm by weight)) of volatile components.

A second polyethylene recovery and volatile removal system can comprise (A) a heated fluidized bed flash chamber for heating and for reducing the pressure of an ethylene polymer effluent stream from an ethylene polymerization reactor, and for removing an initial portion of volatile components from polymer solids, wherein the heated fluidized bed flash chamber is configured to form the polymer solids at a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature of the ethylene polymerization reactor, and (B) a purge column for contacting the polymer solids with a stripping gas, wherein the purge column is configured to remove a final portion of the volatile components to produce a polymer solids stream containing less than <NUM> wt% (<NUM> ppmw) of volatile components.

Generally, the features of the first and second systems (e.g., the flash chamber, the fluidized bed heater, the purge column, and the heated fluidized bed flash chamber, among others) are independently described herein and these features can be combined in any combination to further describe the disclosed systems for polyethylene recovery and volatile removal. Moreover, additional components or devices can be present in these systems, and can be utilized without limitation and in any combination to further describe the first and second systems for polyethylene recovery and volatile removal, unless stated otherwise.

Referring now to the first system, in which the system includes a flash chamber for reducing the pressure of an ethylene polymer effluent stream - containing polymer solids and volatile components - from an ethylene polymerization reactor. While not limited thereto, the volatile content of the ethylene polymer effluent stream can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, volatile components (e.g., nitrogen, ethylene, comonomer if used, hydrogen if used, inert hydrocarbon condensing agent, etc.) when the ethylene polymerization reactor is a gas phase reactor. The volatile content is normally much higher when the ethylene polymerization reactor is a loop slurry reactor, and the volatile content of the ethylene polymer effluent stream often can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, of volatile components (e.g., ethylene, comonomer if used, hydrogen if used, hydrocarbon diluent such as isobutane, etc.).

When the ethylene polymerization reactor is a gas phase reactor, the flash chamber can reduce the pressure to about <NUM> to <NUM> kPa (about <NUM> about <NUM> psig), or to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig), and after the first portion of the volatile components is removed, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components. The polymer solids resulting from the flash chamber typically can have a solids temperature that is from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), or from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), less than the reaction temperature in the ethylene polymerization reactor, when the ethylene polymerization reactor is a gas phase reactor.

When the ethylene polymerization reactor is a loop slurry reactor, the flash chamber can reduce the pressure to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig, to about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig) (low pressure flash), or to about <NUM> to about <NUM> kPa (about <NUM> about <NUM> psig (high pressure flash)), and after the first portion of the volatile components is removed, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components. The polymer solids in the flash chamber typically have a solids temperature that is from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than the reaction temperature in the ethylene polymerization reactor. In some instances, the resultant polymer solids often are part of an exit stream from the flash chamber in which the pressure is further reduced to about <NUM> kPa (about <NUM> psig), about <NUM> kPa (about <NUM> psig), or about <NUM> kPa (about <NUM> psig). The resultant polymer solids exiting the flash chamber typically can have a solids temperature that is from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), or from about <NUM> (<NUM> °F) to about <NUM> (<NUM> °F), less than the reaction temperature in the ethylene polymerization reactor, when the ethylene polymerization reactor is a loop slurry reactor.

The polymer solids from the flash chamber can be fluidized while heating in the fluidized bed heater, which can increase the solids temperature from at least about <NUM> (<NUM> °F) above the solids temperature exiting the flash chamber and up to about <NUM> (<NUM> °F) greater than the reaction temperature. Further, a second portion of the volatile components can be removed in the fluidized bed heater. While volatile removal is not the primary objective of the fluidized bed heater, any suitable amount of volatile components can be removed, for example, the polymer solids resulting from fluidized bed heater can contain from about <NUM>% to about <NUM>%, or from about <NUM>% to about <NUM>%, less volatile components than the polymer solids exiting the flash chamber.

Beneficially, the residence time in the fluidized bed heater is relatively short. The residence time in the fluidized bed heater typically can fall within a range of from about <NUM> minute to about <NUM> minutes, from about <NUM> minute to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable fluidizing gas can be used in the fluidized bed heater. For instance, the polymer solids can be fluidized with a fluidizing gas comprising nitrogen (or other inert gas), ethylene, flash chamber gas, a recycled fraction of the second portion of the volatile components removed in the fluidized bed heater, and the like, as well as combinations thereof. The flash chamber gas can be a portion of the volatile components removed from the polymer solids and exiting the flash chamber. The temperature of the fluidizing gas is not particularly limited, so long as the gas temperature is sufficient to significantly increase the temperature of the polymer solids. Often, the fluidizing gas temperature ranges from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature.

The fluidized bed heater can increase the solids temperature from at least about <NUM> (<NUM> °F) above (or from at least about <NUM> (<NUM> °F) above, or from at least about <NUM> (<NUM> °F) above) the solids temperature exiting the flash chamber, and up to about <NUM> (<NUM> °F) greater (or up to about <NUM> (<NUM> °F) greater, or up to about <NUM> (<NUM> °F) greater) than the reaction temperature.

In the purge column, the polymer solids - which are heated in the fluidized bed heater - can be contacted with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm) by weight of volatile components. In one example, the third portion of volatile components is removed to form the polymer solids stream containing less than about <NUM> wt% (<NUM> ppmw of volatile components, while in another example, the polymer solids stream contains less than about <NUM> wt% (<NUM> ppmw) of volatile components, and in yet another example, the polymer solids stream contains less than about <NUM> wt% (<NUM> ppmw) of volatile components.

The purge column generally operates at relatively low pressures. For instance, the purge column can be operated at a pressure in a range from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (<NUM> psig), or from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig). The residence time in the purge column typically is any time period sufficient to reduce the volatile content to a desired amount (e.g., less than <NUM> wt% (<NUM> ppmw), less than <NUM> wt% (<NUM> ppmw), etc.), and due to the much higher solids temperature resulting from the fluidized bed heater, the residence time in the purge column can be from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes. Moreover, more than one purge column can be present in the system, such as two purge columns arranged in series or parallel.

Any suitable stripping gas can be used in the purge column. For instance, the polymer solids can be contacted with a stripping gas comprising nitrogen (or other inert gas), ethylene, and the like, as well as combinations thereof. The temperature of the stripping gas is not particularly limited, but often contacts the polymer solids at a temperature that is from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature. In some examples, stripping gas at ambient temperature and up to about <NUM> (<NUM> °F) can be used.

Referring now to the second system, in which the ethylene polymer effluent stream from the ethylene polymerization reactor contains polymer solids and volatile components. Similar to the first system, and while not limited thereto, the volatile content of the ethylene polymer effluent stream in the second system can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, volatile components when the ethylene polymerization reactor is a gas phase reactor. The volatile content is normally much higher when the ethylene polymerization reactor is a loop slurry reactor, and the volatile content of the ethylene polymer effluent stream can range from about <NUM> to about <NUM> wt. %, or from about <NUM> to about <NUM> wt. %, of volatile components.

In the second system, the effluent stream enters a heated fluidized bed flash chamber, which is configured for heating and for reducing the pressure of the effluent stream, and which removes an initial portion of volatile components from the polymer solids. The resultant polymer solids can have a solids temperature from about <NUM> (<NUM> °F) less to about <NUM> (<NUM> °F) greater than a reaction temperature in the ethylene polymerization reactor. The heated fluidized bed flash chamber reduces the pressure to any suitable pressure, but generally the pressure is in a range from about <NUM> to <NUM> kPa (about <NUM> about <NUM> psig) in some examples, and from about <NUM> to <NUM> kPa (about <NUM> to about <NUM> psig) in other examples.

After the initial portion of the volatile components is removed via the heated fluidized bed flash chamber, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components, when the ethylene polymerization reactor is a gas phase reactor. When the ethylene polymerization reactor is a loop slurry reactor, the resultant polymer solids can contain from about <NUM> to about <NUM> wt. % volatile components, or from about <NUM> to about <NUM> wt. % volatile components.

The resultant polymer solids exiting the heated fluidized bed flash chamber - after fluidizing and heating at a reduced pressure - can have a significantly increased temperature. Often, the solids temperature can be from about <NUM> (<NUM> °F) less (or from about <NUM> (<NUM> °F) less, or from about <NUM> (<NUM> °F) less) than the reaction temperature in the ethylene polymerization reactor, and up to about <NUM> (<NUM> °F) greater (or up to about <NUM> (<NUM> °F) greater, or up to about <NUM> (<NUM> °F) greater) than the reaction temperature.

Beneficially, the residence time in the heated fluidized bed flash chamber is relatively short. The residence time typically falls within a range of from about <NUM> minute to about <NUM> minutes, from about <NUM> minute to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable fluidizing gas can be used in the heated fluidized bed flash chamber. For instance, the polymer solids can be fluidized with a fluidizing gas comprising nitrogen (or other inert gas), ethylene, a recycled fraction of the initial portion of the volatile components removed in the heated fluidized bed flash chamber, and the like, as well as combinations thereof. The temperature of the fluidizing gas is not particularly limited, so long as the gas temperature is sufficient to significantly increase the temperature of the polymer solids. Often, the fluidizing gas temperature ranges from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature.

The purge column in the second system can be configured as described above for the purge column in the first system. Thus, the purge column is configured to contact the polymer solids - which are heated in the fluidized bed flash chamber - with a stripping gas to remove a final portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm) by weight of volatile components; alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components; alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components; or alternatively, less than about <NUM> wt% (<NUM> ppmw) of volatile components. The purge column can be operated at relatively low pressures: for example, from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (<NUM> psig), or from about <NUM> kPa (about <NUM> psig) to about <NUM> kPa (about <NUM> psig). The residence time in the purge column generally is any time period sufficient to reduce the volatile content to a desired amount (e.g., less than <NUM> wt% (<NUM> ppmw), less than <NUM> wt% (<NUM> ppmw), etc.), and due to the much higher solids temperature resulting from the heated fluidized bed flash chamber, the residence time in the purge column typically falls within a range of from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, from about <NUM> minutes to about <NUM> minutes, or from about <NUM> minutes to about <NUM> minutes.

Any suitable stripping gas can be used in the purge column. Therefore, the polymer solids can be contacted with a stripping gas comprising nitrogen (or other inert gas), ethylene, and the like, as well as combinations thereof. The temperature of the stripping gas is not particularly limited, but often contacts the polymer solids at a temperature that is from about <NUM> (<NUM> °F) less than to about <NUM> (<NUM> °F) greater than the reaction temperature. In some examples, stripping gas at ambient temperature and up to about <NUM> (<NUM> °F) can be used.

Both the first and second systems for polyethylene recovery and volatile removal can further include an extruder for converting the polymer solids stream into solid polymer pellets. Typically, a pelletizing extruder or other suitable device can be used. This disclosure is also directed to, and encompasses, the solid polymer pellets produced by any of the volatile removal systems and polymerization reactor systems disclosed herein.

Optionally, the systems can further include an injector for introducing a catalyst deactivating agent (e.g., water) into the ethylene polymer effluent stream prior to the flash chamber. While the catalyst deactivating agent can be added at this location in the systems, other options may be more beneficial. For instance, the stripping gas can further include a catalyst deactivating agent (e.g., air), or alternatively, the fluidizing gas can further comprise a catalyst deactivating agent, in both the first and second systems.

In another example, the first and second systems can further comprise an injector for introducing a catalyst deactivating agent (e.g., air) into the polymer solids stream after the purge column, for instance, before converting into solid polymer pellets with an extruder.

Referring now to <FIG>, which illustrates a polyethylene recovery and volatile removal system <NUM>. The system <NUM> can include a flash chamber <NUM>, a fluidized bed heater <NUM>, a purge column <NUM>, and an extruder <NUM>. Related to the system <NUM> is a reactor <NUM>, such as a gas phase or loop slurry reactor, from which an effluent stream <NUM> enters the flash chamber <NUM> in the polyethylene recovery and volatile removal system <NUM>. While not limited thereto, typical reaction temperatures in the reactor are in the <NUM> to <NUM> (<NUM> to <NUM> °F) range for HDPE grades, and in the <NUM> to <NUM> (<NUM> to <NUM> °F) range for LLDPE grades.

For a loop slurry reactor, the composition of the effluent stream <NUM> is a slurry containing ethylene polymer solids and approximately <NUM> to <NUM> wt. % volatile components, inclusive of diluent (e.g., isobutane) and residual monomer/comonomer. Some of the volatile components are entrained/absorbed into the ethylene polymer solids. For a gas phase reactor, the composition of the effluent stream <NUM> is polymer solids and approximately <NUM> to <NUM> wt. % volatile components, inclusive of a fluidizing gas and residual monomer/comonomer. As with loop slurry, some of the volatile components are entrained/absorbed into the ethylene polymer solids.

In the case of a loop slurry reactor, the effluent stream <NUM> can include a heated pipe - e.g., with an outer jacket containing a heating medium, such as steam - but is generally not heated for gas phase processes. Optionally, a catalyst deactivating agent can be added into effluent stream <NUM>. Often, the catalyst deactivating agent is water, but is not limited thereto. While the catalyst deactivating agent can be added at this stage of the process, it often is avoided because any hydrocarbon-containing streams that are to be recycled to the reactor have to be purified to remove the catalyst deactivating agent (i.e., to avoid deactivating the catalyst in the reactor <NUM>). This can involve sophisticated and expensive purification means, such as molecular sieve beds, distillation, and the like. Moreover, the equipment can be quite large and expensive due to the size of the recycle stream at this stage of the process.

In <FIG>, the flash chamber <NUM> often operates at approximately <NUM> to <NUM> (<NUM> to <NUM> °F) less than the reaction temperature for gas phase processes and at a pressure of approximately <NUM> to <NUM> kPa (about <NUM> to <NUM> psig), while for loop slurry processes, the flash chamber <NUM> typically operates at approximately <NUM> to <NUM> (<NUM> to <NUM> °F) less than the reaction temperature and at a higher pressure of approximately <NUM> to <NUM> kPa (about <NUM> to <NUM> psig). Any suitable design for the flash chamber can be used, and volatile removal and solid product separation can be achieved using a cyclone design, separation by gravity, or any combination of the two together. Stream <NUM> is the volatile stream that exits the flash chamber (flash chamber gas).

The stream <NUM> exiting the flash chamber <NUM> enters the fluidized bed heater <NUM>. After exiting the flash chamber <NUM> and prior to entering the fluidized bed heater <NUM>, the volatile content of stream <NUM> has been reduced significantly, as compared to effluent stream <NUM>. For a loop slurry reactor, stream <NUM> often contains ethylene polymer particles and generally <NUM> to <NUM> wt. % volatile components, whereas for a gas phase reactor, stream <NUM> often contains ethylene polymer particles and generally <NUM> to <NUM> wt. % volatile components. Some of the volatile components are entrained/absorbed into the ethylene polymer particles. In most cases, the stream <NUM> leaving the flash chamber <NUM> has lower volatile content from a gas phase reactor than from a loop slurry reactor.

Volatile removal often results in a temperature drop in the flash chamber <NUM>, and in stream <NUM> if there is a significant pressure drop from flash chamber <NUM> to fluidized bed heater <NUM>. The ethylene polymer particles in stream <NUM> have a temperature that is typically <NUM> to <NUM> (<NUM> to <NUM> °F) less than the reaction temperature for loop slurry, and typically <NUM> to <NUM> (<NUM> to <NUM> °F) less than the reaction temperature for gas phase. Temperature drop in the flash chamber for gas phase is generally not nearly as significant as for loop slurry. Optionally, stream <NUM> can include a heated pipe, similar to effluent stream <NUM>, particularly for loop slurry processes. Temperature rise is very limited, due in part to space/distance limitations, pressure drop considerations, liquid hydrocarbons to vaporize, and the like.

The fluidized bed heater <NUM> is designed to increase the temperature of the solid ethylene polymer particles in stream <NUM> prior to the entering the purge column <NUM> via stream <NUM>. Unexpectedly, it was found that even an increase in temperature of ~<NUM> (~<NUM> °F) over stream <NUM> can be significant and beneficial. The residence time of the ethylene polymer particles in the fluidized bed heater <NUM> is relatively short, often from <NUM> to <NUM> minutes, or from <NUM> to <NUM> minutes. The particles are fluidized by hot fluidizing gas <NUM> (e.g., at reaction temperature or about <NUM> (<NUM> °F) greater than the reaction temperature), which can contain nitrogen, ethylene, and the like, as well as the gas <NUM> that exits the flash chamber. Combinations of more than one source for the fluidizing gas can be used. The fluidizing gas exiting <NUM> the heater <NUM> can be recycled or re-used.

The fluidized bed heater <NUM> can operate at any suitable pressure, and can be in the same pressure ranges as noted above for the flash chamber, as well as lower pressures. While not a primary focus of the heater <NUM>, an additional portion of volatiles that are entrained/absorbed into the solids particles can be removed, and these volatiles depart with the fluidizing gas exiting <NUM> the heater <NUM>.

Beneficially, feed stream <NUM> contains solid ethylene polymer particles that have an elevated solids temperature at the entrance of the purge column <NUM>. It is beneficial for there to be at least a <NUM> (<NUM> °F) increase in temperature of the solid particles - as compared to line <NUM> exiting the flash chamber <NUM>. More desirable is a temperature of the polymer solids in stream <NUM> which is at or above the reaction temperature, such as up to approximately <NUM> to <NUM> (<NUM> to <NUM> °F) greater than the reaction temperature. Compositionally, stream <NUM> contains solid polymer particles with a volatile content somewhat less than in stream <NUM>, often by approximately <NUM> to <NUM>% on a relative percent basis.

The purge column <NUM> generally operates at low pressure, from ambient to about <NUM> kPa (<NUM> psig) in some examples, and from ambient to about <NUM> kPa (about <NUM> psig) in other examples. If the solids temperature is not sufficiently high to facilitate significant volatile removal (to less than <NUM> wt% (<NUM> ppmw), or to less than <NUM> wt% (<NUM> ppmw)), the residence time can be unacceptable high (e.g., <NUM>-<NUM> hours). Further, the column size can be very large and the volume of stripping gas exceedingly large as well. With the increased solids temperature due to the fluidized bed heater <NUM>, the residence time can be reduced to about <NUM>-<NUM> minutes, the column size can be reduced (smaller purge columns), and significantly less stripping gas is required.

The temperature of the stripping gas <NUM> entering the purge column can be generally near the reaction temperature, for example, within <NUM> (<NUM> °F) above or below the reaction temperature. The stripping gas can comprise nitrogen and/or ethylene, but is not limited thereto, and can be recovered in an exit stream <NUM> and re-used.

Optionally, a catalyst deactivating agent can be present in the stripping gas <NUM> in the purge column. Alternatively, a catalyst deactivating agent can be present in the fluidizing gas <NUM>. Air or a small percentage of oxygen can be used, although other catalyst deactivating agents can be used.

Polymer solids stream <NUM> exits the purge column <NUM> and contains less than <NUM> wt% (<NUM> ppmw) of volatile components. In some instances, the volatile content of the polymer solids stream <NUM> can be less than <NUM>, less than <NUM>, or less than <NUM> wt% (less than <NUM>, less than <NUM>, or less than <NUM> ppmw). The polymer solids stream <NUM> is fed to the extruder <NUM> to form solid polymer pellets <NUM>. Optionally, a catalyst deactivating agent (e.g., air) can be added to the polymer solids stream <NUM> prior to extrusion/pelletizing.

Referring now to <FIG>, which illustrates another polyethylene recovery and volatile removal system <NUM>. The system <NUM> can include a heated fluidized bed flash chamber <NUM>, a purge column <NUM>, and an extruder <NUM>. Related to the system <NUM> is a reactor <NUM>, such as a gas phase or loop slurry reactor, from which an effluent stream <NUM> enters the heated fluidized bed flash chamber <NUM> in the polyethylene recovery and volatile removal system <NUM>. The reactor <NUM>, effluent <NUM>, purge column <NUM>, extruder <NUM>, and streams <NUM>, <NUM>, <NUM>, and <NUM> are generally the same as described for the similarly numbered components in <FIG>.

In <FIG>, the heated fluidized bed flash chamber <NUM> often operates at a pressure in a range of from <NUM> to <NUM> kPa (<NUM> to <NUM> psig), or from <NUM> to <NUM> kPa (about <NUM> to <NUM> psig). Any suitable design for the heated fluidized bed flash chamber can be used, and volatile removal and solid product separation can be achieved using a cyclone design, with or without separation by gravity. Stream <NUM> is the volatile stream that exits the flash chamber.

The stream <NUM> exiting the heated fluidized bed flash chamber <NUM> enters the purge column <NUM>. After exiting the heated fluidized bed flash chamber <NUM> and prior to entering the purge column <NUM>, the volatile content of stream <NUM> has been reduced significantly, as compared to effluent stream <NUM>. For a loop slurry reactor, stream <NUM> often contains ethylene polymer particles and generally <NUM> to <NUM> wt. % volatile components, whereas for a gas phase reactor, stream <NUM> often contains ethylene polymer particles and generally <NUM> to <NUM> wt. % volatile components. Some of the volatile components are entrained/absorbed into the ethylene polymer particles.

The heated fluidized bed flash chamber <NUM> is designed to increase the temperature of the solid ethylene polymer particles in stream <NUM> prior to the entering the purge column. Beneficially, feed stream <NUM> contains solid ethylene polymer particles that have an elevated solids temperature at the entrance of the purge column <NUM>. Often, the solids temperature is approximately <NUM> (<NUM> °F) less than the reaction temperature to at or above the reaction temperature, such as up to approximately <NUM> to <NUM> (<NUM> to <NUM> °F) greater than the reaction temperature. The residence time of the ethylene polymer particles in the heated fluidized bed flash chamber <NUM> is relatively short, often from <NUM> to <NUM> minutes, or from <NUM> to <NUM> minutes. The particles are fluidized by hot fluidizing gas <NUM> (e.g., at reaction temperature or about <NUM> (<NUM> °F) greater than the reaction temperature), which can contain nitrogen, ethylene, and the like, as well as the gas <NUM> that exits the heated fluidized bed flash chamber <NUM>. Combinations of more than one source for the fluidizing gas can be used. The fluidizing gas exiting <NUM> the heated fluidized bed flash chamber <NUM> can be recycled or re-used.

Also encompassed herein are ethylene polymerization processes and polymerization reactor systems. An ethylene polymerization process can comprise (<NUM>) contacting a catalyst composition with ethylene and an optional olefin comonomer in an ethylene polymerization reactor under polymerization reaction conditions in a polymerization reactor system to produce an ethylene polymer effluent stream, and (<NUM>) conducting any method for removing volatile components from the ethylene polymer effluent stream disclosed herein. A polymerization reactor system can comprise (<NUM>) any polyethylene recovery and volatile removal system disclosed herein, and (<NUM>) the ethylene polymerization reactor, wherein the ethylene polymerization reactor is configured to contact a catalyst composition with ethylene and an optional olefin comonomer to produce the ethylene polymer effluent stream.

The polymerization processes and reactor systems disclosed herein are applicable to any catalyst composition or catalyst system (e.g., any transition metal-based catalyst system) suitable for the polymerization of an olefin monomer, such as ethylene. The catalyst system can comprise, for example, a transition metal (one or more than one) from Groups <NUM>-<NUM> of the Periodic Table of the Elements. In one example, the catalyst composition can comprise a Group <NUM>, <NUM>, or <NUM> transition metal, or a combination of two or more transition metals. The catalyst system can comprise chromium, titanium, zirconium, hafnium, vanadium, or a combination thereof, in some examples, or can comprise chromium, titanium, zirconium, hafnium, or a combination thereof, in other examples. Accordingly, the catalyst composition can comprise chromium, or titanium, or zirconium, or hafnium, either singly or in combination. Thus, catalyst compositions comprising two or more transition metal compounds, wherein each transition metal compound independently can comprise chromium, titanium, zirconium, hafnium, vanadium, or a combination thereof, are contemplated and encompassed herein.

Various catalyst compositions known to a skilled artisan are useful in the polymerization of olefins. These include, but are not limited to, Ziegler-Natta based catalyst systems, chromium-based catalyst systems, metallocene-based catalyst systems, non-metallocene based catalyst systems (or post-metallocene based catalyst systems), and the like, including combinations thereof. The polymerization processes and reactor systems disclosed herein are not limited to the aforementioned catalyst systems, but nevertheless, particular examples directed to these catalyst systems are contemplated. Hence, the catalyst composition can be a Ziegler-Natta based catalyst system, a chromium-based catalyst system, and/or a metallocene-based catalyst system; alternatively, a Ziegler-Natta based catalyst system; alternatively, a chromium-based catalyst system; alternatively, a metallocene-based catalyst system; or alternatively, a non-metallocene based catalyst system (or a post-metallocene based catalyst system). In one example, the catalyst composition can be a dual catalyst system comprising at least one metallocene compound, while in another example, the catalyst composition can be a dual catalyst system comprising two different metallocene compounds.

Examples of representative and non-limiting catalyst compositions include those disclosed in <CIT>,<CIT>,<CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT>,<CIT>,<CIT>, <CIT>, and<CIT>.

In some examples, the catalyst composition, in addition to a transition metal compound, can contain an activator and an optional co-catalyst. Illustrative activators can include, but are not limited to, aluminoxane compounds, organoboron or organoborate compounds, ionizing ionic compounds, activator-supports (e.g., solid oxides treated with an electron-withdrawing anion), and the like, or combinations thereof. Commonly used polymerization co-catalysts can include, but are not limited to, metal alkyl, or organometal, co-catalysts, with the metal encompassing boron, aluminum, and the like. For instance, alkyl boron and/or alkyl aluminum compounds often can be used as co-catalysts in a transition metal-based catalyst system. Representative compounds can include, but are not limited to, tri-n-butyl borane, tripropylborane, triethylborane, trimethylaluminum (TMA), triethylaluminum (TEA), tri-n-propylaluminum (TNPA), tri-n-butylaluminum (TNBA), triisobutylaluminum (TIBA), tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminum ethoxide, diethylaluminum chloride, and the like, including combinations thereof. In these and other examples, the transition metal compound can comprise a metallocene compound and/or a chromium compound. The metallocene compound can be a bridged metallocene or an unbridged metallocene compound.

In some examples, the transition metal-based catalyst composition can comprise (or consist essentially of, or consist of) a transition metal supported on, impregnated onto, and/or mixed or cogelled with a carrier. The transition metal compound, whether a metallocene compound, chromium compound, or other, can be supported on, impregnated onto, and/or mixed or cogelled with any of a number of porous carriers including, but not limited to, solid oxides, activator-supports (chemically-treated solid oxides), molecular sieves and zeolites, clays and pillared clays, and the like. For example, the transition metal-based catalyst composition can comprise chromium impregnated onto silica, chromium impregnated onto silica-titania, chromium impregnated onto aluminophosphate, chromium cogelled with silica, chromium cogelled with silica-titania, or chromium cogelled with aluminophosphate, and this includes any combinations of these materials.

In some examples, the catalyst composition can comprise a metallocene catalyst component, while in other examples, the catalyst composition can comprise a first metallocene catalyst component and a second metallocene catalyst component. The catalyst systems can contain an activator and, optionally, a co-catalyst. Any metallocene component of the catalyst compositions provided herein can, in some examples, comprise an unbridged metallocene; alternatively, an unbridged zirconium or hafnium based metallocene compound; alternatively, an unbridged zirconium or hafnium based metallocene compound containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and an indenyl group; alternatively, an unbridged zirconium based metallocene compound containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and an indenyl group. Illustrative and non-limiting examples of unbridged metallocene compounds (e.g., with zirconium or hafnium) that can be employed in catalyst systems are described in <CIT>, <CIT>, <CIT>, and <CIT>.

In other examples, any metallocene component of the catalyst compositions provided herein can comprise a bridged metallocene compound, e.g., with titanium, zirconium, or hafnium, such as a bridged zirconium based metallocene compound with a fluorenyl group, and with no aryl groups on the bridging group, or a bridged zirconium based metallocene compound with a cyclopentadienyl group and a fluorenyl group, and with no aryl groups on the bridging group. Such bridged metallocenes, in some examples, can contain an alkenyl substituent (e.g., a terminal alkenyl) on the bridging group, on a cyclopentadienyl-type group (e.g., a cyclopentadienyl group or a fluorenyl group), or on the bridging group and the cyclopentadienyl-type group. In another example, the metallocene catalyst component can comprise a bridged zirconium or hafnium based metallocene compound with a fluorenyl group, and an aryl group on the bridging group; alternatively, a bridged zirconium or hafnium based metallocene compound with a cyclopentadienyl group and fluorenyl group, and an aryl group on the bridging group; alternatively, a bridged zirconium based metallocene compound with a fluorenyl group, and an aryl group on the bridging group; or alternatively, a bridged hafnium based metallocene compound with a fluorenyl group, and an aryl group on the bridging group. In these and other examples, the aryl group on the bridging group can be a phenyl group. Optionally, these bridged metallocenes can contain an alkenyl substituent (e.g., a terminal alkenyl) on the bridging group, on a cyclopentadienyl-type group, or on both the bridging group and the cyclopentadienyl group. Illustrative and non-limiting examples of bridged metallocene compounds (e.g., with zirconium or hafnium) that can be employed in catalyst systems are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

In the polymerization processes and reactor systems disclosed herein, the catalyst composition can be contacted with ethylene (to form an ethylene homopolymer) or with ethylene and an olefin comonomer (to form an ethylene copolymer, ethylene terpolymer, etc.). Suitable olefin comonomers can include, but are not limited to, propylene, <NUM>-butene, <NUM>-butene, <NUM>-methyl-<NUM>-butene, isobutylene, <NUM>-pentene, <NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-hexene, <NUM>-hexene, <NUM>-ethyl-<NUM>-hexene, <NUM>-heptene, <NUM>-heptene, <NUM>-heptene, <NUM>-octene, <NUM>-decene, styrene, and the like, or combinations thereof. According to one example, the olefin comonomer can comprise an α-olefin (e.g., a C<NUM>-C<NUM> α-olefin), while in another example, the comonomer can comprise propylene, <NUM>-butene, <NUM>-pentene, <NUM>-hexene, <NUM>-octene, <NUM>-decene, styrene, or any combination thereof; or alternatively, the olefin comonomer can comprise <NUM>-butene, <NUM>-hexene, <NUM>-octene, or a combination thereof.

Accordingly, in the polymerization processes and reactor systems disclosed herein, the ethylene polymer effluent stream (or polymer solids, or polymer solids stream, or solid polymer pellets) can comprise an ethylene homopolymer and/or an ethylene/α-olefin copolymer (e.g., a C<NUM>-C<NUM> α-olefin) in one example, and can comprise an ethylene homopolymer, an ethylene/<NUM>-butene copolymer, an ethylene/<NUM>-hexene copolymer, and/or an ethylene/<NUM>-octene copolymer in another example.

The disclosed processes and systems are intended for any polymerization process and reactor system in which an ethylene polymer effluent stream is discharged from a gas phase reactor or a loop slurry reactor. Thus, the ethylene polymerization reactor in the disclosed processes and systems can comprise a gas phase reactor or, alternatively, a loop slurry reactor. The polymerization conditions for these reactor types are well known to those of skill in the art. Gas phase reactors can comprise fluidized bed reactors or staged horizontal reactors. Slurry reactors can comprise vertical or horizontal loops. The reactor can be operated batchwise or continuously, and continuous processes can use intermittent or continuous product discharge. Polymerization reactor systems and processes also can include partial or full direct recycle of unreacted monomer, unreacted comonomer (if used), or diluent (if used).

The polymerization reactor system can comprise a single reactor (gas phase or loop slurry) or multiple reactors (for example, <NUM> reactors, or more than <NUM> reactors). For instance, the polymerization reactor system can comprise multiple loop reactors, multiple gas phase reactors, or a combination of loop and gas phase reactors (e.g., in series). Thus, the polymerization reactor system can comprise a series of a loop reactor followed by a gas phase reactor, or a series of a gas phase reactor followed by a loop slurry reactor, or a series of a gas phase reactor followed by the polyethylene recovery and volatile removal system and then followed by another reactor (e.g., a loop slurry reactor), and so forth.

According to one example, the polymerization reactor system can comprise at least one loop slurry reactor comprising vertical or horizontal loops. Monomer, diluent (if used), catalyst, and comonomer (if used) can be continuously fed to a loop reactor where polymerization occurs. Generally, continuous processes can comprise the continuous introduction of monomer (and comonomer, if used), catalyst, and diluent into a polymerization reactor and the continuous removal from this reactor of a suspension comprising polymer particles and the diluent. In some examples, the wt. % solids (based on reactor contents) in the loop reactor often can range from about <NUM> wt. % to about <NUM> wt. %, or from about <NUM> wt. % to about <NUM> wt. In other examples, the wt. % solids in the loop reactor can be less than about <NUM> wt. %, less than about <NUM> wt. %, or less than about <NUM> wt. %, such as from about <NUM> wt. % to about <NUM> wt. %, or from about <NUM> wt. % to about <NUM> wt. The ethylene polymer effluent stream can contain, for instance, solid polymer, diluent, ethylene, and comonomer.

A typical slurry polymerization process (also known as the particle form process) is disclosed, for example, in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, and <CIT>.

Suitable diluents used in slurry polymerization include, but are not limited to, the monomer being polymerized and hydrocarbons that are liquids under reaction conditions. Examples of suitable diluents include, but are not limited to, hydrocarbons such as propane, cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, and n-hexane. Some loop polymerization reactions can occur under bulk conditions where no diluent is used, such as can be employed in the bulk polymerization of propylene to form polypropylene homopolymers.

According to yet another example, the polymerization reactor system can comprise at least one gas phase reactor (e.g., a fluidized bed reactor). Such reactor systems can employ a continuous recycle stream containing one or more monomers continuously cycled through a fluidized bed in the presence of the catalyst under polymerization conditions. A recycle stream can be withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, an ethylene polymer effluent stream can be withdrawn from the reactor and new or fresh monomer can be added to replace the polymerized monomer. Such gas phase reactors can comprise a process for multi-step gas-phase polymerization of olefins, in which olefins are polymerized in the gaseous phase in at least two independent gas-phase polymerization zones while feeding a catalyst-containing polymer formed in a first polymerization zone to a second polymerization zone. One type of gas phase reactor is disclosed in <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

According to still another example, the polymerization reactor system can comprise a high pressure polymerization reactor, e.g., can comprise a tubular reactor or an autoclave reactor. Tubular reactors can have several zones where fresh monomer, initiators, or catalysts are added. Monomer can be entrained in an inert gaseous stream and introduced at one zone of the reactor. Initiators, catalysts, or catalyst components can be entrained in a gaseous stream and introduced at another zone of the reactor. The gas streams can be intermixed for polymerization. Heat and pressure can be employed appropriately to obtain optimal polymerization reaction conditions.

According to yet another example, the polymerization reactor system can comprise a solution polymerization reactor wherein the monomer/comonomer are contacted with the catalyst composition by suitable stirring or other means. A carrier comprising an inert organic diluent or excess monomer can be employed. If desired, the monomer/comonomer can be brought in the vapor phase into contact with the catalytic reaction product, in the presence or absence of liquid material. The polymerization zone can be maintained at temperatures and pressures that will result in the formation of a solution of the polymer in a reaction medium. Agitation can be employed to obtain better temperature control and to maintain uniform polymerization mixtures throughout the polymerization zone. Adequate means are utilized for dissipating the exothermic heat of polymerization.

Polymerization conditions that can be controlled for efficiency and to provide desired polymer properties can include temperature, pressure, and the concentrations of various reactants. Polymerization temperature can affect catalyst productivity, polymer molecular weight, and molecular weight distribution. Various polymerization conditions can be held substantially constant, for example, for the production of a particular grade of the olefin polymer. A suitable polymerization reaction temperature can be any temperature below the de-polymerization temperature according to the Gibbs Free energy equation. Typically, this includes from about <NUM> to about <NUM>, for example, or from about <NUM> to about <NUM>, depending upon the type of polymerization reactor. In some reactor systems, the polymerization reaction temperature generally can be within a range from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

Suitable pressures will also vary according to the reactor and polymerization type. The pressure for liquid phase polymerizations in a loop reactor typically can be less than <NUM> MPa (<NUM> psig). The pressure for gas phase polymerization can be in the <NUM> MPa (<NUM> psig) to <NUM> MPa (<NUM> psig) range. High pressure polymerization in tubular or autoclave reactors generally can be conducted at about <NUM> MPa (<NUM>,<NUM> psig) to <NUM> MPa (<NUM>,<NUM> psig). Polymerization reactors also can be operated in a supercritical region occurring at generally higher temperatures and pressures (for instance, above <NUM> and <NUM> MPa (<NUM> psig)). Operation above the critical point of a pressure/temperature diagram (supercritical phase) can offer advantages to the polymerization reaction process.

Constructive Example <NUM> is based on a mathematical model of the polyethylene recovery and volatile removal system shown in <FIG>. A HDPE can be produced in a gas phase reactor <NUM> at a reaction temperature of <NUM> (<NUM> °F). The effluent stream <NUM> from the gas phase reactor <NUM> contains HDPE solids and <NUM> wt. % volatile components, and enters the flash chamber <NUM> operating at a temperature of <NUM> to <NUM> (<NUM> to <NUM> °F), and HDPE solids with <NUM> wt. % volatiles exit the flash chamber <NUM> via stream <NUM> at nominally the same temperature, approximately <NUM> (<NUM> °F). After contact with fluidizing gas <NUM> to <NUM> (<NUM> at <NUM> °F) and a residence time of <NUM>-<NUM> minutes in fluidized bed heater <NUM>, the exiting polymer solids <NUM> are increased in temperature by at least <NUM> (<NUM> °F) (to ~<NUM> (~<NUM> °F)) over stream <NUM>, and up to a temperature of about <NUM> (<NUM> °F). Thus, instead of entering the purge column <NUM> directly from the flash chamber <NUM> via stream <NUM> at ~<NUM> (~<NUM> °F), the polymer solids enter the purge column <NUM> from the fluidized bed heater <NUM> via stream <NUM> at a solids temperature of at least <NUM> (<NUM> °F) and up to <NUM> (<NUM> °F). In the purge column <NUM>, the HDPE solids are contacted with stripping gas <NUM> at a temperature of <NUM> (<NUM> °F) for a residence time of <NUM> minutes, reducing the volatile content in the polymer solids stream <NUM> to less than <NUM> wt% (<NUM> ppmw).

Claim 1:
A method for removing volatile components from an ethylene polymer effluent stream from an ethylene polymerization reactor, the method comprising:
(i) reducing a pressure of the effluent stream to remove a first portion of the volatile components from polymer solids, the polymer solids having a solids temperature from <NUM> (<NUM> °F) to <NUM> (<NUM> °F) less than a reaction temperature in the ethylene polymerization reactor;
(ii) fluidizing the polymer solids and heating the polymer solids to a solids temperature from at least <NUM> (<NUM> °F) above the solids temperature in step (i) and up to <NUM> (<NUM> °F) greater than the reaction temperature, and wherein a second portion of the volatile components are removed; and
(iii) contacting the polymer solids with a stripping gas to remove a third portion of the volatile components to form a polymer solids stream containing less than <NUM> wt% (<NUM> ppm by weight (ppmw)) of volatile components.