RU2783377C1 - Systems and methods for reducing heat exchanger pollution rate - Google Patents

Abstract

FIELD: heat exchangers.

SUBSTANCE: invention relates to systems and methods for reducing the fouling rate of a heat exchanger. The system for reducing the fouling rate of the heat exchanger comprises: a gas outlet line configured to pass the first gas stream. The first heat exchanger is configured to receive the first gas stream and obtain the first cooled gas stream. A bypass line configured to remove a portion of the entrained fine polyolefin particles from the gas outlet line to form a bypass stream and combine it with the second gas stream at the outlet of the bypass line. The bypass line inlet is located upstream of the first heat exchanger. The bypass line outlet is located downstream of the first heat exchanger.

EFFECT: reducing the rate of fouling of the heat exchanger.

20 cl, 10 dwg, 2 tbl

Description

FIELD OF TECHNOLOGY

[0001] This disclosure relates generally to systems and methods for reducing the fouling rate of a heat exchanger.

BACKGROUND OF THE INVENTION

[0002] Gas phase polyolefin reactor systems, such as fluidized bed reactor systems, are often configured to recycle at least a portion of the gases from the reactor. In particular, gas phase polyolefin reactor systems often separate solid polyolefin particles from an effluent gas stream, pass the separated gas stream through one or more heat exchangers to cool the separated gas stream, and recycle the cooled gas stream to the polyolefin reactor. However, over time, solid polyolefin particles tend to accumulate in one or more heat exchangers. The accumulation of solid polyolefin particles fouls one or more heat exchangers and increases the pressure drop in one or more heat exchangers, and also reduces the efficiency of one or more heat exchangers. As soon as the pressure drop across the heat exchanger(s) exceeds a certain value, the capacity of the piece of equipment is limited by that pressure drop, with higher pressure drops leading to a reduction in performance. Due to reduced unit production caused by fouling of the heat exchanger, it is often necessary to shut down the entire reactor system, such as once every 6 months for 7 or more days, to clean the heat exchangers and restore them to optimum efficiency at significant cost to the operator.

[0003] Accordingly, improved reactor systems and methods are needed.

SUMMARY OF THE INVENTION

[0004] The present disclosure provides systems and methods having a design that reduces this heat exchanger fouling problem. Thus, this disclosure provides a method for reducing a fouling rate of a heat exchanger, comprising: supplying a first gas stream containing gas and entrained fine polyolefin particles to an exhaust line; preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0005] According to a further aspect, this disclosure provides a system for reducing a fouling rate of a heat exchanger, comprising: an exhaust line configured to pass a first gas stream containing gas and entrained fine polyolefin particles; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a first cooled gas stream; and a bypass line configured to preferentially remove a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; wherein the bypass line comprises a bypass line inlet and a bypass line outlet, wherein the bypass line inlet is located upstream of the first heat exchanger, while the bypass line outlet is located downstream of the first heat exchanger, and the bypass line is configured such that the bypass flow combined with a second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0006] According to a further aspect, this disclosure provides a process for polymerizing olefins, comprising: contacting one or more olefins with a catalyst under polymerization conditions in a polymerization reactor to form a first gas stream containing solid fine particles and unreacted olefins; supplying the first gas stream to the exhaust line; preferentially removing a portion of the solid fine particles from the vent line to form a bypass stream containing a higher concentration of solid fine particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0007] According to a further aspect, this disclosure provides an olefin polymerization system comprising: a polymerization reactor for contacting one or more olefins with a catalyst under polymerization conditions to form a first gas stream containing solid fine particles and unreacted olefins; a gas outlet line configured to receive the first gas stream; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a cooled gas stream; a bypass line configured to preferentially remove a portion of the solid fine particles from the gas outlet line to form a bypass stream containing a higher concentration of solid fine particles, the bypass line comprising an inlet and an outlet, the inlet being located upstream of the first heat exchanger, the outlet located downstream of the first heat exchanger, and wherein the bypass line is configured such that the bypass stream is combined with the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and the temperature of the combined gas stream is below the dew point of the combined gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The file of the patent or application contains at least one graphic material, made in color. Copies of this patent or patent application with color graphic(s)(s) will be made available by the Patent Office upon request and upon payment of the applicable fee.

[0009] The following graphics are part of this specification and are included to further demonstrate certain aspects of this disclosure. The invention may be better understood with reference to one or more of these drawings in combination with a detailed description of the specific aspects presented herein.

[0010] FIG. 1 is a diagram of a system and process for the polymerization of olefins in accordance with an aspect of the present disclosure.

[0011] FIG. 2 is a diagram of a system and process for the polymerization of olefins in accordance with another aspect of the present disclosure.

[0012] FIG. 3A illustrates a partial view of a substantially hemispherical bend in a vent line, a bypass line inlet, and a bypass line in accordance with an aspect of the present disclosure.

[0013] FIG. 3B illustrates a partial cross-sectional view according to FIG. 3A.

[0014] FIG. 4 illustrates the process gas temperature along the first and second heat exchangers in a system according to an embodiment of the present disclosure.

[0015] FIG. 5 illustrates the cooling capacity along the first and second heat exchangers in a system according to an embodiment of the present disclosure.

[0016] FIG. 6 illustrates polymer particle trajectories in a system according to an embodiment of the present invention.

[0017] FIG. 7 illustrates polymer particle trajectories in a system according to an embodiment of the present invention.

[0018] FIG. 8 illustrates polymer particle velocity vectors at the inlet of a bypass line in a system according to an embodiment of the present disclosure.

[0019] FIG. 9 illustrates polymer particle velocity vectors at the inlet of a bypass line in a system according to an embodiment of the present disclosure.

[0020] FIG. 10 illustrates a partially transparent view of a substantially hemispherical bend in a vent line, a bypass line inlet, and a bypass line in accordance with an aspect of the present disclosure.

[0021] Although the inventions disclosed herein are susceptible to various modifications and alternative forms, only a few specific embodiments are shown by way of example in the drawings and are described in detail below. The drawings and detailed descriptions of these specific embodiments are in no way intended to limit the breadth or scope of the inventive ideas or the appended claims. Rather, the graphics and detailed written descriptions are provided to illustrate the inventive concepts to a person skilled in the art and to enable such person to create and use the inventive concepts.

DEFINITIONS

[0022] The following definitions are provided to assist those skilled in the art in understanding the detailed description of the present invention. Unless otherwise indicated herein, scientific and technical terms used in connection with the present invention have the meanings traditionally understood by those of ordinary skill in the art to which this invention belongs, and unless otherwise indicated or the context otherwise requires, these definitions apply throughout this disclosure. In addition, unless the context otherwise requires, terms used in the singular include the plural, and terms used in the plural include the singular.

[0023] If a term is used in this disclosure but is not specifically defined herein, then the definition from the IUPAC Compendium of Chemical Terminology, 2nd Edition (1997) may apply, provided that this definition does not conflict with any other disclosure or applicable herein definition, or does not make undefined or prohibit any claim to which this definition applies. To the extent that any definition or use provided in any document incorporated herein by reference conflicts with a definition or use provided herein, the definition or use provided herein shall control.

[0024] Unless expressly stated otherwise in certain circumstances, all percentages, parts, ratios, and like amounts used herein are by weight.

[0025] In addition, in this regard, some features of the invention, which for clarity are described herein in the context of separate embodiments, can also be provided in combination in one embodiment. Conversely, various features of the invention, which for brevity are described in the context of one embodiment, may also be provided separately or in any subcombination.

[0026] With regard to transitional terms or phrases of claims, the transitional term "comprising", which is synonymous with the terms "comprising", "having in composition" or "characterized", is inclusive or unrestricted, and does not exclude additional elements not listed or method steps. The transitional expression "consisting of" excludes any element, step, or ingredient not listed in a claim. The transitional expression "consisting essentially of" limits the scope of the claim to the specified materials or steps and those that do not significantly affect the essential and novel features of the claimed invention. A claim "consisting essentially of" is intermediate between closed claims written in the "consisting of" format and fully open claims written in the "comprising" format. Unless otherwise indicated when describing a compound or composition, the term "consisting essentially of" is not to be construed as "comprising", but is intended to describe the specified component, including materials that do not significantly alter the composition or method to which the applied term refers. For example, a feedstock consisting essentially of material A may include impurities normally present in a commercially prepared or commercially available sample of said compound or composition. When an application includes different features and/or classes of features (e.g., process step, feedstock features, and/or product features, among other possibilities), the transition terms containing, consisting essentially of, and consisting of apply only to the class features to which they apply, and different transitional terms or phrases with different features may be used in the claims. For example, the method may include several of the steps listed (and other steps not listed), but use catalyst system preparation consisting of specific steps, and use a catalyst system containing the listed components and other non-listed components. Although compositions and methods are described as "comprising" various components or steps, compositions and methods can also "consist essentially of" or "consist of" various components or steps.

[0027] The articles "a" and "an" can be used in connection with various elements and components of the compositions, processes or structures described herein. This is for convenience and to give a general idea of compositions, processes, or designs. Such a description includes "one or at least one" of the elements or components. Moreover, as used herein, articles in the singular also include a description of a plurality of elements or components, unless the specific context implies that the plural is excluded.

[0028] The terms "optional" or "optional" mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not occur.

[0029] The terms "made to be used" or "made to be used" and similar language are used herein to indicate that a particular design or procedure listed is used in an olefin polymerization system or process as disclosed herein. For example, unless otherwise indicated, a particular design "capable of use" means that it is "capable of use in an olefin polymerization reactor system" and, therefore, is designed, formed, configured, constructed, and/or intended to perform polymerization of olefins, as will be understood by a person skilled in the art.

[0030] The terms "fine particles", "solid fine particles", "polyolefin fine particles", etc. are used interchangeably herein to refer to solid polyolefin particles. In one aspect, the polyolefin fine particles may have an aerodynamic diameter of about or less than 250 microns (microns), 5 microns, 10 microns, 20 microns, 50 microns, 75 microns, or 200 mesh. Although the term "polymer" may be associated with the term "fine particles", this term is intended to cover any particulate matter in the gas stream in question, including catalyst or prepolymer particles that may be loaded into the reactor, growing polymer particles, agglomerated polymer particles and flakes or exfoliation of polymer particles. In some embodiments, the size of the polymer particles in the process may include, but are not limited to, the following sizes: Group A, 30-100 microns; Group B, 100-1000 microns; Group C, 0-30 microns. The polymer should not be construed as being limited to any particular particle size distribution.

[0031] The term "olefin" is used herein in accordance with the definition given by IUPAC: acyclic and cyclic hydrocarbons having one or more carbon-carbon double bonds in addition to formal bonds in aromatic compounds. The class "olefins" includes alkenes and cycloalkenes and the corresponding polyenes. Ethylene, propylene, 1-butene, 2-butene, 1-hexene, etc. are non-limiting examples of olefins. The term "alpha-olefin" (α-olefin) refers to an olefin that has a double bond between the first and second carbon atoms of the longest continuous chain of carbon atoms. The term "alpha-olefin" includes linear and branched alpha-olefins, unless expressly stated otherwise.

[0032] In describing a range of measurements, such as angles, etc., Applicant intends to disclose every single number that such a range can reasonably cover, for example, every single number that has at least one significant digit more than expandable endpoint of the range. For example, when talking about an angle between 60° and 70°, it is understood that the angle can be 60°, 61°, 62°, 63°, 64°, 65°, 66°, 67°, 68°, 69 ° or 70°, including any sub-ranges or combinations of sub-ranges included in this wider range. Applicant's intention is for these two range description methods to be interchangeable. Moreover, when a range of values is disclosed or claimed, Applicant also intends that the range disclosure reflects and is interchangeable with the disclosure of any and all subranges and combinations of subranges covered by it. Accordingly, Applicant reserves the right to specify or exclude any individual members of any such group, including any subranges or combinations of subranges within a group, or any selection, feature, range, element, or aspect that may be claimed if, for any reason, Applicant decides to claim less than full disclosure, for example, to account for a reference that the applicant may not have been aware of at the time of filing. In addition, the ranges specified herein include their endpoints, unless expressly stated otherwise. In addition, when an amount, concentration, or other value or parameter is specified as a range, one or more preferred ranges, or a list of upper preferred values and lower preferred values, this should be understood as a specific disclosure of all ranges formed from any pair of any upper range limit. or a preferred value and any lower range limit or preferred value, whether or not such pairs are disclosed separately. The scope of the invention is not limited to the specific values specified in the definition of the range.

[0033] The term "about" means that quantities, sizes, compositions, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or more or less, as desired, reflecting tolerances, conversion factors , rounding off, measurement errors, and the like, as well as other factors known to those skilled in the art. In general, an amount, size, composition, parameter, or other quantity or characteristic is "about" or "approximate" whether or not it is expressly stated. The term "about" also covers amounts that differ due to different equilibrium conditions for the composition obtained from a particular initial mixture. Whether modified by the term "about", the claims include equivalents to the quantities indicated. The term "about" can mean within 10% of the reported numerical value, or within 5% of the reported numerical value, or within 2% of the reported numerical value.

[0034] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "comprises", or "comprising", or any their other variations are intended to cover non-exclusive inclusions in the invention. For example, a composition, mixture, process, method, article, or apparatus that contains a list of elements is not necessarily limited to only those elements, but may include other elements not explicitly stated or inherent in such composition, mixture, process, method, article, or apparatus. Also, unless otherwise explicitly stated, "or" refers to an inclusive "or" but not to an exclusive "or". For example, condition A or B is satisfied by any of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present) .

[0035] As used herein, the term "bringing into contact" refers to the process of bringing into contact at least two different species so that they can respond. However, it should be understood that the end product of the reaction may be obtained directly from the reaction between the added reactants or from an intermediate product from one or more added reactants that can be obtained in the reaction mixture.

[0036] The terms "substantial" and "substantially" as used herein are intended to give their ordinary and generally accepted meaning to a person skilled in the art (and should not be limited to a special or individual meaning), including, without limitation, referring to a substantially perpendicular arrangement that differs from a perpendicular arrangement by up to ±10°.

DETAILED DESCRIPTION

[0037] The drawings described above and the written description of specific structures and functions below are not intended to limit the scope of Applicants' invention or the scope of the appended claims. Rather, these graphics and written description are provided for the instruction of any person of ordinary skill in the art to make and use the present invention, for which patent protection is sought. Those skilled in the art will appreciate that, for purposes of clarity and understanding, not all features of a commercial embodiment of the inventions have been described or shown. Those skilled in the art will also appreciate that the development of an actual commercial embodiment incorporating aspects of the present invention will require numerous implementation-specific decisions to achieve the developer's ultimate goal for said commercial embodiment. Such implementation decisions may include, and are likely not limited to, compliance with system, business, governmental, and other restrictions, which may vary by implementation, location, and from time to time. While the developer's effort may be complex and time consuming in an absolute sense, such effort will nonetheless be a routine task for those skilled in the art using this disclosure. It should be understood that the inventions disclosed and set forth herein are susceptible to numerous and varied modifications and alternative forms. In conclusion, the use of a term in the singular, such as the singular indefinite article "a" among other things, is not intended as a limitation on the number of elements. In addition, the use of relative terms such as, but not limited to, "top", "bottom", "left", "right", "top", "bottom", "down", "up", "side" and the like, used in the present description for clarity in specific reference to the drawings and is not intended to limit the scope of the present invention or the appended claims.

[0038] In one aspect of the present disclosure, a method is provided for reducing a fouling rate of a heat exchanger, comprising: supplying a first gas stream containing gas and entrained fine polyolefin particles to an exhaust line; preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0039] In another aspect of the present disclosure, a system for reducing a fouling rate of a heat exchanger is provided, comprising: an exhaust line configured to pass a first gas stream containing gas and entrained fine polyolefin particles; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a first cooled gas stream; and a bypass line configured to preferentially remove a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; wherein the bypass line comprises a bypass line inlet and a bypass line outlet, wherein the bypass line inlet is located upstream of the first heat exchanger, while the bypass line outlet is located downstream of the first heat exchanger, and the bypass line is configured such that the bypass flow combined with a second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0040] In another aspect of the present disclosure, a process for polymerizing olefins is provided, comprising: contacting one or more olefins with a catalyst under polymerization conditions in a polymerization reactor to form a first gas stream containing solid fine particles and unreacted olefins; supplying the first gas stream to the exhaust line; preferentially removing a portion of the solid fine particles from the vent line to form a bypass stream containing a higher concentration of solid fine particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0041] In accordance with another aspect of the present disclosure, an olefin polymerization system is provided, comprising: a polymerization reactor for contacting one or more olefins with a catalyst under polymerization conditions to form a first gas stream containing solid fine particles and unreacted olefins; a gas outlet line configured to receive the first gas stream; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a cooled gas stream; a bypass line configured to preferentially remove a portion of the solid fine particles from the gas outlet line to form a bypass stream containing a higher concentration of solid fine particles, the bypass line comprising an inlet and an outlet, the inlet being located upstream of the first heat exchanger, the outlet located downstream of the first heat exchanger, and wherein the bypass line is configured such that the bypass stream is combined with the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0042] In some embodiments, the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen, and one or more paraffins. For example, in some embodiments, the first gas stream includes unreacted olefins such as ethylene, propylene, 1-butene, 2-butene, 1-hexene, or any combination thereof. In some embodiments, the first gas stream includes paraffins such as ethane, propane, butane, pentane, isopentane, hexane, or any combination thereof. In some embodiments, the finely divided polyolefin particles comprise homopolymers, copolymers, terpolymers, and the like. In some embodiments, the fine polyolefin particles comprise polyethylene. In some embodiments, the finely divided polyolefin particles comprise ethylene homopolymers and ethylene copolymers and at least one alpha-olefin wherein the ethylene content is at least about 50% by weight of the total monomers involved. Examples of alpha-olefins that can be used are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, 1 -hexadecene and the like. Polyenes such as 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene may also be used herein. -2-norbornene, 5-vinyl-2-norbornene and olefins formed in situ in the polymerization medium. When olefins are formed in situ in the polymerization medium, the formation of polyethylenes containing long chain branches can occur.

[0043] In some embodiments, polyolefin particles are produced using a catalyst. In the present disclosure, any catalyst suitable for the polymerization of olefins may be used. For example, the olefin polymerization catalyst may include at least one metal selected from Groups 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13 of the Periodic Table of the Elements. Examples of metals are titanium, zirconium, hafnium, scandium, vanadium, iron, chromium, nickel and aluminum. The olefin polymerization catalyst may be neutral or cationic.

[0044] Examples of such polymerization catalysts include, but are not limited to:

[0045] [1] Catalyst compounds and compositions containing a Group 6 element such as chromium, examples of which include, but are not limited to, chromium oxide catalysts and organochromium catalysts that can be supported and/or activated;

[0046] [2] Ziegler-Natta catalysts and compositions of all types, which typically contain a transition metal component and a co-catalyst such as an organoaluminum compound;

[0047] [3] metallocene catalysts of all types as used herein to refer to substituted and unsubstituted mono(cyclopentadienyl) and bis(cyclopentadienyl) transition metal catalysts and analogs of such compounds such as pentadienyl, pyrrole, boratabenzene, etc. p., usually also comprising an organometallic cocatalyst such as an alumoxane (such as methylalumoxane), an alkyl or aryl aluminum compound, or an alkyl or aryl substituted boron compound;

[0048] [4] any catalytic compound containing a group 13 element, such as compounds containing aluminum;

[0049] [5] Catalyst compounds and compositions containing a Group 10 element, for example, a nickel-containing catalyst, such as cationic nickel-alkyldiimine complexes, often used in combination with an organometallic co-catalyst;

[0050] [6] Group 8 element containing catalyst compounds and compositions such as iron compounds, which may also optionally include an organometallic cocatalyst such as an alkylalumoxane or other organoaluminum or organoboron compound;

[0051] [7] Any compound containing a Group 4 element, such as compounds containing titanium and zirconium, examples of which include cationic or neutral titanium and zirconium compounds, and which may also include an organometallic cocatalyst such as an alkylalumoxane or other organoaluminum or organoboron compound; and

[0052] [8] An olefin polymerization catalyst that polymerizes olefins to produce olefin interpolymers having a molecular weight distribution (MWD) of 1 to 2.5.

[0053] In some embodiments, the above catalysts may be supported on any particulate carriers known in the art.

[0054] In some aspects, the fine polyolefin particles have an average diameter of less than about 200 microns, less than about 150 microns, less than about 100 microns, less than about 50 microns, less than about 10 microns, or any combination of these ranges, or any ranges between them. For example, in some aspects, the finely divided polyolefin particles have an average diameter of about 200 microns, about 195 microns, about 190 microns, about 180 microns, about 175 microns, about 170 microns, about 165 microns, about 160 microns, about 155 microns, about 145 µm, approx. 140 µm, approx. 135 µm, approx. 130 µm, approx. 125 µm, approx. 120 µm, approx. 115 µm, approx. 110 µm, approx. , approx. 80 µm, approx. 75 µm, approx. 70 µm, approx. 65 µm, approx. 60 µm, approx. 55 µm, approx. 50 µm, approx. 20 µm, approx. 15 µm, approx. 10 µm, approx. 9 µm, approx. 8 µm, approx. 7 µm, approx. 6 µm, approx. 5 µm, approx. 4 µm, approx. them.

[0055] In some aspects, the method further includes supplying the first cooled gas stream to a second heat exchanger that produces a second cooled gas stream. In some aspects, the system further comprises a second heat exchanger downstream of the first heat exchanger, wherein the second heat exchanger is configured to provide a second cooled gas stream. That is, in some aspects, the second heat exchanger is located downstream of the first heat exchanger.

[0056] In some aspects, the outlet of the bypass line is located upstream of the second heat exchanger, and the second gas stream is the first cooled gas stream. That is, in some aspects, the bypass line is configured to bypass the fine polyolefin particles around the first heat exchanger. In some aspects, the method further includes supplying the second cooled gas stream to a compressor to form a compressed gas stream.

[0057] In some aspects, the exit of the bypass line is located downstream of the second heat exchanger, and the second gas stream is a second cooled gas stream. That is, in some aspects, the bypass line is configured to bypass the fine polyolefin particles around both the first and second heat exchangers. In some aspects, the method further includes providing the first cooled gas stream to a compressor to form a compressed gas stream; and supplying the compressed gas stream to the second heat exchanger. In some aspects, the system further comprises a compressor configured to compress the first cooled gas stream to form a compressed gas stream that is fed to the second heat exchanger.

[0058] In some aspects, the system may further include one or more adjustable valves at the inlet of the bypass line or at the outlet of the bypass line, configured to control the flow rate of the bypass flow. For example, in some aspects, the system includes a bypass line outlet variable valve configured to control the bypass flow rate. In some aspects, the method may further include adjusting one or more valves upstream of the bypass line or downstream of the bypass line to control the flow rate of the bypass stream. For example, in some aspects, the method may include adjusting a bypass line outlet valve to control the bypass flow rate. In some aspects, the valve may be a butterfly valve, gate valve, or ball valve.

[0059] In some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream comprises removing from about 5 wt. % to about 75 wt. % of the first gas stream, for example, about 5 wt. %, about 10 wt. %, about 15 wt. %, about 20 wt. %, about 25 wt. %, about 30 wt. %, about 35 wt. %, about 40 wt. %, about 45 wt. %, about 50 wt. %, about 55 wt. %, about 60 wt. %, about 65 wt. %, about 70 wt. %, about 75 wt. %, or any range in between.

[0060] Surprisingly, in some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the gas outlet line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream results in an overall loss in cooling capacity of about 1 % to about 20%, such as about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, or any range in between. Without wishing to be bound by any particular theory, it is believed that bypassing a portion of the vent line around the first heat exchanger results in a loss of cooling capacity of the first heat exchanger. After the bypass portion is recombined with the gas outlet, the higher temperature of the combined gas results in an increase in the cooling capacity of the second heat exchanger so that the overall cooling capacity is not reduced as much as it would be without the bypass.

[0061] In some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream results in a loss in cooling capacity of the first heat exchanger of about 5%. up to about 150%, for example, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55% , about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 100%, about 105%, about 110%, about 115%, about 120%, about 125%, about 130%, about 135%, about 140%, about 145%, about 150%, or any range in between. Without wishing to be bound by any particular theory, it is believed that bypassing part of the vent line around the first heat exchanger results in a loss in cooling capacity of the first heat exchanger.

[0062] In some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the gas outlet line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream results in a reduction in the cooling capacity of the second heat exchanger from about 5%. up to about 50%, e.g., about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, or any range between them. Without wishing to be bound by any particular theory, it is believed that bypassing a portion of the vent line around the first heat exchanger and combining the bypass portion downstream of the first heat exchanger at a higher temperature prior to being fed into the second heat exchanger results in increased cooling capacity of the second heat exchanger.

[0063] In some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than present in the first gas stream results in reduced fouling in the first heat exchanger. Without wishing to be bound by any particular theory, it is believed that bypassing a portion of the vent line with its associated fine polyolefin particles around the first heat exchanger results in fewer fine particles reaching the first heat exchanger, which in turn results in reduced fouling.

[0064] In some aspects, the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream results in no change in fouling in the second heat exchanger. Without intending to be bound by any particular theory, it is believed that the significantly reduced fouling in the second heat exchanger may be due to the "flushing" effect that the first cooled gas stream or the second cooled gas stream can have on any solid polyolefin particles. In particular, it is believed that some of the first cooled gas stream and/or the second cooled gas stream may exit the first heat exchanger and/or the second heat exchanger in liquid form, and that some of these liquids may remove or wash fine polymer particles from the heat exchanger and associated pipelines with it. For example, liquid pentane and hexene are known to wash solid polyethylene particles. When operated without a bypass, there is "flushing" in the pipeline downstream of the first heat exchanger and the second heat exchanger, indicating little polymer buildup on any surface between cleanings. Conversely, all surfaces of the pipelines upstream of the first heat exchanger and in the first heat exchanger up to a certain point exposed to the process gas show a significant accumulation of polymer between cleanings. Thus, without intending to be bound by any particular theory, it is believed that if the temperature of the combined gas stream entering the second heat exchanger is below the dew point of the gas, then this stream will serve to flush any fine polyolefin particles from the second heat exchanger or downstream pipeline. and systems. Thus, flushing serves to keep the downstream heat exchanger clean so that its performance (especially pressure drop) does not deteriorate significantly over time, even if the upstream heat exchanger fouls and more gas bypasses the upstream heat exchanger.

[0065] In some aspects, the bypass stream is configured to receive or preferentially remove or contains up to about 80 wt. % entrained fine polyolefin particles in the first gas stream, for example, from about 5 wt. % to about 75 wt. % of the first gas stream, for example, about 5 wt. %, about 10 wt. %, about 15 wt. %, about 20 wt. %, about 25 wt. %, about wt. %, about 35 wt. %, about 40 wt. %, about 45 wt. %, about 50 wt. %, about 55 wt. %, about 60 wt. %, about 65 wt. %, about 70 wt. %, about 75 wt. %, about 80 wt. % or any range in between.

[0066] In some aspects, the vent line comprises a substantially hemispherical bend. By "substantially hemispherical" is meant that the vent line contains a bend that extends through the full arc of the semicircle, that is, is 180° or within ±10° of the full arc of the semicircle. Without wishing to be bound by any particular theory, it is believed that passage of the gaseous effluent stream through a substantially hemispherical bend may favor the separation of the entrained fine polyolefin particles to form a bypass stream. That is, it is believed that the centripetal force acting on the fine polyolefin particles as they pass through the substantially hemispherical bend can preferentially separate the fine polyolefin particles to the inner surface of the exhaust line, which is at the outermost part of the bend. Advantageously, by positioning the inlet of the bypass line near the outermost part of the bend, these particles can then advantageously separate from the vent line to form a bypass stream. For example, in some aspects, the bypass line is tangential to the hemispherical bend. That is, in some aspects the bypass line runs tangentially to the outermost part of the bend. In some aspects, the bypass line is at an angle to the hemispherical bend. For example, in some aspects, the bypass line is at an angle of about 30 degrees to about 90 degrees from a line bisecting a substantially hemispherical bend, such as about 30 degrees, about 35 degrees, about 40 degrees, about 45 degrees, about 50 degrees. degrees, about 55 degrees, about 60 degrees, about 65 degrees, about 70 degrees, about 75 degrees, about 80 degrees, about 85 degrees, about 90 degrees, or any range in between.

[0067] In some aspects, the inlet of the bypass line includes an intake extending into the vent line. That is, in some aspects, the inlet of the bypass line includes a protrusion extending into the vent line to assist in the removal of fine polyolefin particles.

[0068] In some aspects, the bypass line has an internal diameter that is from about 10% to about 40% of the internal diameter of the flue line, for example, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, or any range in between. For example, in some aspects, the bypass line has an internal diameter that is about 33% of the internal diameter of the vent line, for example, the bypass line may have an internal diameter of 12 inches while the vent line has an internal diameter of 36 inches.

[0069] In some aspects, the inlet of the bypass line has an internal diameter that is from about 5% to about 50% larger than the internal diameter of the bypass line, for example, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50% or any range in between. For example, in some aspects, the bypass line inlet has an inside diameter that is 50% larger than the bypass line inside diameter, for example, the bypass line inlet may have an inside diameter of 18 inches at its widest point and then decrease to the bypass line inside diameter. , which is 12 inches. Without intending to be bound by any particular theory, it is believed that a larger internal diameter of the bypass line inlet can lead to an increase in the efficiency of preferential separation of polyolefin particles compared to a bypass line inlet having the same diameter as the bypass line.

[0070] In some aspects, the method further includes supplying the first gas stream to a fine particle separator in fluid communication with the polymerization reactor and the vent line to separate the first portion of the solid fine particles from unreacted olefins prior to supplying the first gas stream to the vent line; and supplying the first portion of the solid fine particles to an eductor in fluid communication with the fine particle separator to move the first portion of the solid fine particles back to the polymerization reactor. In some aspects, the system further includes a fine particle separator in fluid communication with the polymerization reactor and a vent line configured to separate a first portion of the particulate matter from unreacted olefins prior to the first gas stream being fed into the vent line. In some aspects, the system further includes an eductor in fluid communication with the fine particle separator to convey the first portion of the solid fine particles back to the polymerization reactor. For example, in some aspects, the eductor may be an eductor as described in US Patent Application No. 15/730,314, which is incorporated herein by reference in its entirety.

[0071] In some aspects, the eductor comprises a first tubular body having a hollow interior and containing a first inlet and a first outlet spaced from the first inlet along a central axis, and a side wall surrounding the central axis and defining a mixing chamber; and a second tubular body having a hollow interior and comprising a second inlet and a second outlet spaced therefrom, wherein the second tubular body extends into the mixing chamber through a side wall of the first tubular body between the first inlet and the first outlet, the second inlet being oriented substantially perpendicularly axis of the first tubular body, wherein the second tubular body comprises a first bend less than 90° from the perpendicular to the first outlet before passing into the mixing chamber, and the second tubular body comprises a second bend less than 90° to the first outlet after passing into the mixing chamber.

Illustrated Embodiments

[0072] FIG. 1 is a diagram of a system and process for the polymerization of olefins in accordance with an aspect of the present disclosure. The olefin-containing inlet stream 101 is fed to a polymerization reactor 103 where the olefins are polymerized to form a polymerization reactor outlet stream 105, which contains solid polyolefin particles and unreacted olefins, and a solid polyolefin product stream 137. Inlet stream 101 and outlet stream 105 may include any suitable olefin, a combination of olefins, and in some embodiments, may include additional components such as catalysts, polymerization initiators, chain length agents, and the like, as will be appreciated by those skilled in the art.

[0073] The polymerization reactor effluent 105 is then fed to a cyclone 107 where it is separated into a gas stream 113, which contains entrained fine solid polyolefin particles, and a solid fine particle stream 116. Fine particulate stream 116 is then introduced into eductor 109 along with driving gas 131. In some embodiments, the inlet of eductor 301 is directly adjacent to the particulate outlet at the bottom of the cyclone, although this is not required.

[0074] Part of the gas stream 113 passes to the first heat exchanger 115, while a part of the gas stream 113, which includes a predominantly separated part of the solid polyolefin particles, is separated into the bypass line 117. In the first heat exchanger, the first cooled gas stream 119 is obtained, and the bypass stream 117 combines with the first cooled gas stream 119 to form a combined stream 121, which is fed to the second heat exchanger 123 to obtain a second cooled gas stream 125. The temperature of the combined stream 121 is below the dew point of the combined gas stream 121. The second cooled gas stream 125 is fed to the compressor 127 , in which a compressed gas stream 129 is obtained. A portion of the compressed gas stream is supplied to the eductor 109 as driving gas 131, as discussed above. A portion of the pressurized gas stream 129 is fed into a liquid separation vessel 133, in which a liquid stream 137 and a gas stream 135 are obtained, which are recycled to the polymerization reactor 103.

[0075] FIG. 2 is a diagram of a system and process for the polymerization of olefins in accordance with another aspect of the present disclosure. The olefin-containing inlet stream 201 is fed to a polymerization reactor 203 where the olefins are polymerized to form a polymerization reactor effluent 205, which contains solid polyolefin particles and unreacted olefins, and a solid polyolefin product stream 237. Inlet stream 201 and outlet stream 205 may include any suitable olefin, a combination of olefins, and in some embodiments, may include additional components such as catalysts, polymerization initiators, chain length agents, and the like, as will be appreciated by those skilled in the art.

[0076] The polymerization reactor effluent 205 is then fed to a cyclone 207 where it is separated into a gas stream 213, which contains entrained fine solid polyolefin particles, and a solid fine particle stream 216. The particulate matter stream 216 is then introduced into the eductor 209 along with the driving gas 231. In some embodiments, the inlet of the eductor 201 is directly adjacent to the particulate outlet at the bottom of the cyclone, although this is not required.

[0077] A portion of the gas stream 213 passes to the first heat exchanger 215, while a portion of the gas stream 213, which includes a predominantly separated portion of the solid polyolefin particles, is separated into a bypass line 217. In the first heat exchanger, a first cooled gas stream 225 is obtained, which is fed into compressor 227 to produce compressed gas stream 219 which is fed to second heat exchanger 223 to produce second cooled gas stream 221. Bypass stream 217 combines with second cooled gas stream 221 to form combined stream 229 having a temperature that is below the dew point of the combined gas stream 121. A portion of the combined gas stream 229 is fed to the eductor 209 as driving gas 231, as discussed above. A portion of the combined gas stream 229 is fed to a liquid separation vessel 233, which produces a liquid stream 237 and a gas stream 235, which is recycled to the polymerization reactor 203.

[0078] FIG. 3A and 3B illustrate partial views of a substantially hemispherical bend in a vent line and a bypass line inlet in accordance with an aspect of the present disclosure. Fig. 3B is a cross-sectional view of a substantially hemispherical bend according to FIG. 3A taken in the plane of the bend along the line b-b. These figures show the hemispherical bend of vent line 314 and bypass line 319 including a bypass line inlet 317 whose inside diameter is larger than that of bypass line 319. Bypass line inlet 317 further includes an intake 318 that extends into the inside diameter of vent line 313 , to further assist in preferentially separating the solid polyolefin particles 314 from the vent line 313 and into the bypass line 319 further, as illustrated in these figures, the inlet of the bypass line is located at an angle θ from line a, which bisects a substantially hemispherical bend.

[0079] FIG. 10 illustrates a partially transparent view of a substantially hemispherical bend in vent line 1013, bypass line inlet 1017, and bypass line 1019 in accordance with an aspect of the present disclosure. In particular, this figure illustrates the inlet 1017 of the bypass line, which is at an angle θ to the line a, which is parallel to the line bisecting the essentially hemispherical bend, but is not tangent to the outer surface of the essentially hemispherical bend. The bypass line inlet 1017 further includes an intake 1018 that extends into the interior of the vent line 1013. As shown in this figure, the intake may simply be in the form of an extension of the bypass line inlet 1017. For example, a bypass line inlet can be formed by cutting a pipe at an angle and connecting said pipe to a vent line such that one end of the pipe is substantially flush with the vent line and the other side of the vent line extends into the interior of the vent line. For example, in some embodiments, the vent line may have an inside diameter that is about 50% of the inside diameter of the vent line, and the intake may extend into the inside of the vent line for about 1/ ^9th of the inside diameter. For example, in one embodiment, the inlet of the bypass line may have an internal diameter of about 18 inches, the vent line may have an internal diameter of about 36 inches, and the intake may extend into the interior of the vent line for about 4 inches.

EXAMPLES

[0080] The invention is further illustrated by the examples below, which should in no way be construed as limiting the scope of this invention. Various other aspects, embodiments, modifications, and equivalents, as may occur to one of ordinary skill in the art upon reading the present disclosure, without departing from the spirit of the present invention or the scope of the appended claims.

Example 1: Mathematical Modeling of a Heat Exchanger Fouling Reduction System

[0081] ASPEN EDR software available from ApenTech and ANSYS® FLUENT software were used to simulate a dual heat exchanger system with a bypass line bypassing the first heat exchanger. In this study, two identical shell and tube heat exchangers were arranged in series with process gas flowing on the tube side and cooling water flowing countercurrent on the shell side. Both heat exchangers had 2229 1 inch diameter tubes that were 38 feet long. In this example, the flow rate of the process gas entering the heat exchanger was 1,800,000 pounds per hour (lb/hour) at a temperature of 206.5°F. The cooling water flow is 24,000 gallons per minute (GPM) at 100.6°F. Process gas had the following composition: 5.0 mol. % hydrogen, 28.3 mol. % ethylene, 18.4 mol. % isopentane, 48.0 mol. % nitrogen and 0.3 mol. % 1-hexene. At the beginning of operation, the pressure drop in the first heat exchanger is 2.5 psi. inch, and in the second heat exchanger - 2.0 psi. inch.

[0082] FIG. 4 illustrates the temperature of the process gas along the length of the first heat exchanger on the left side and the second heat exchanger on the right side for various wt. % bypass. In FIG. 5 illustrates the cooling capacity in MMBtu/h in the first heat exchanger on the left side and the second heat exchanger on the right side for various weights. % bypass. As can be seen from these figures, the bypass has relatively little effect on the overall process gas temperature or overall cooling capacity at the end of the second heat exchanger. The data is further shown in Table 1 below. This table shows that the model only predicts an 8.8% reduction in overall cooling capacity at 50% bypass. In addition, at a bypass of 50%, the combined flow entering the second heat exchanger is below the dew point, since 3.3 wt. % liquid. Without wishing to be bound by any particular theory, this is supposed to allow the second heat exchanger to remain clean at 50% bypass as it is still "flushed" with condensed liquid.

[0083] Computational fluid dynamics (CFD) models were used to determine bypass volumes corresponding to various fouling conditions in the first heat exchanger using ANSYS® FLUENT software. Three cases were performed representing fouling conditions at the beginning of the cycle, in the middle of the cycle and at the end of the cycle in the original heat exchanger system (without bypass), provided that the second heat exchanger remains relatively clean. The same fouling conditions were also simulated using a 12" bypass line with an 18" bypass inlet. The particles used to model the polymer particles were 100 µm particles with a density of 0.85 g/cm ³ . The results of these simulations are shown in Table 2. These results confirm that the design of the bypass inlet increases the particle content in the bypass stream. These results also confirm that the pressure drop across the system is significantly lower for a given fouling condition, since the amount of bypass increases as the first heat exchanger fouls. In addition, these results show that at a certain fouling rate of the first heat exchanger, an increase in the length of the section is expected, since the pressure drop in the system is lower under given fouling conditions.

[0084] FIG. 6 and 7 illustrate polymer particle trajectories modeled using CFD. In particular, in FIG. 6 illustrates the polymer particle trajectories at the beginning of the cycle and shows 33 wt. % bypass of particles, and in FIG. 7 illustrates the polymer particle trajectories at the end of the cycle and shows 49 wt. % bypass particles. The particles are entrained in the gas flow and enter from above these figures following a substantially hemispherical bend, and some of the particles are predominantly removed through the tangential bypass line.

[0085] FIG. 8 and 9 illustrate the velocity vectors at the inlet of the bypass line. In particular, in FIG. 8 illustrates the gas velocity vectors at the inlet of the bypass line at the beginning of the cycle and shows 18% gas bypass, while in FIG. 9 illustrates the velocity vectors of polymer particles entering the bypass line at the end of the cycle and shows a gas bypass of 42%. As illustrated in these figures, the bypass flow increases as fouling of the first heat exchanger increases, resulting in lower flow and lower pressure drop in the first heat exchanger.

ASPECTS

[0086] The invention has been described above with reference to numerous aspects and embodiments, as well as specific examples. Many variations will be offered to those skilled in the art in light of the above detailed description. All such obvious variations are within the full scope of the appended claims. Other embodiments of the invention may include, but are not limited to, the following (embodiments are typically described as "comprising" but alternatively may "substantially consist of" or "consist of" unless specifically noted otherwise).

[0087] According to a first aspect of the present disclosure, there is provided a method for reducing a fouling rate of a heat exchanger, comprising: supplying a first gas stream containing gas and entrained fine polyolefin particles to an exhaust line; preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0088] According to a second aspect of the present disclosure, there is provided a process according to the first aspect, wherein the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen, and one or more paraffins.

[0089] According to a third aspect of the present disclosure, there is provided a process according to any of the first or second aspects, wherein the first gas stream contains one or more of pentane, isopentane, hexene, 1-hexene, ethylene, nitrogen, and hydrogen .

[0090] According to a fourth aspect of the present disclosure, there is provided a method according to any one of the first to third aspects, wherein the finely divided polyolefin particles comprise polyethylene.

[0091] According to a fifth aspect of the present disclosure, there is provided a method according to any one of the first to fourth aspects, further comprising supplying a first cooled gas stream to a second heat exchanger that produces a second cooled gas stream.

[0092] According to a sixth aspect of the present disclosure, there is provided a method according to any of the first to fifth aspects, characterized in that the bypass line outlet is located upstream of the second heat exchanger, and wherein the second gas stream is the first cooled gas stream. .

[0093] According to a seventh aspect of the present disclosure, there is provided a method according to any one of the first to sixth aspects, further comprising supplying a second cooled gas stream to a compressor to form a compressed gas stream.

[0094] According to an eighth aspect of the present disclosure, there is provided a method according to any one of the first to seventh aspects, wherein the bypass line outlet is located downstream of the second heat exchanger, and wherein the second gas stream is a second cooled gas stream. .

[0095] According to a ninth aspect of the present disclosure, there is provided a method according to any one of the first to eighth aspects, further comprising supplying a first cooled gas stream to a compressor to form a compressed gas stream; and supplying the compressed gas stream to the second heat exchanger.

[0096] According to a tenth aspect of the present disclosure, there is provided a method according to any one of the first to ninth aspects, further comprising adjusting a bypass line outlet valve to control the bypass flow rate.

[0097] According to an eleventh aspect of the present disclosure, there is provided a method according to any one of the first to tenth aspects, characterized in that the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles particles than is present in the first gas stream, includes the removal of about 5 wt. % to about 75 wt. % of the first gas flow.

[0098] According to a twelfth aspect of the present disclosure, there is provided a method according to any one of the first to eleventh aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles particles than is present in the first gas stream results in a loss in cold performance of about 5% to about 20%.

[0099] According to a thirteenth aspect of the present disclosure, there is provided a method according to any one of the first to twelfth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles particles than present in the first gas stream results in a loss in cooling capacity of the first heat exchanger from about 1% to about 50%.

[0100] According to a fourteenth aspect of the present disclosure, there is provided a method according to any one of the first to thirteenth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles particles than is present in the first gas stream leads to an increase in the cooling capacity of the second heat exchanger, comprising from about 5% to about 150%.

[0101] In accordance with the fifteenth aspect of the present disclosure, a method is provided in accordance with any of the first to fourteenth aspects, characterized in that the bypass stream contains up to about 80 wt. % entrained fine polyolefin particles in the first gas stream.

[0102] According to a sixteenth aspect of the present disclosure, there is provided a method according to any of the first to fifteenth aspects, wherein the fine polyolefin particles have an average diameter of less than about 200 microns.

[0103] According to a seventeenth aspect of the present disclosure, there is provided a method according to any one of the first to sixteenth aspects, wherein the finely divided polyolefin particles have an average diameter of less than about 150 microns.

[0104] According to an eighteenth aspect of the present disclosure, there is provided a method according to any one of the first to seventeenth aspects, wherein the fine polyolefin particles have an average diameter of less than about 10 microns.

[0105] According to a nineteenth aspect of the present disclosure, there is provided a method according to any one of the first to eighteenth aspects, wherein the vent line comprises a substantially hemispherical bend.

[0106] According to a twentieth aspect of the present disclosure, there is provided a method according to any one of the first to nineteenth aspects, characterized in that the bypass line extends tangentially to the hemispherical bend.

[0107] According to the twenty-first aspect of the present disclosure, there is provided a method according to any one of the first to twentieth aspects, wherein the bypass line is at an angle of about 30 degrees to about 90 degrees from a substantially bisecting line. hemispherical bend.

[0108] According to a twenty-second aspect of the present disclosure, there is provided a system for reducing a fouling rate of a heat exchanger, comprising: an exhaust line configured to pass a first gas stream containing gas and entrained fine polyolefin particles; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a first cooled gas stream; and a bypass line configured to preferentially remove a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream; wherein the bypass line comprises a bypass line inlet and a bypass line outlet, wherein the bypass line inlet is located upstream of the first heat exchanger, while the bypass line outlet is located downstream of the first heat exchanger, and the bypass line is configured such that the bypass flow combined with a second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0109] According to the twenty-third aspect of the present disclosure, there is provided a system according to the twenty-second aspect, wherein the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen, and one or more paraffins.

[0110] According to a twenty-fourth aspect of the present disclosure, there is provided a system according to any one of the twenty-second to twenty-third aspects, wherein the first gas stream contains one or more of pentane, isopentane, hexene, 1-hexene, ethylene , nitrogen and hydrogen.

[0111] According to a twenty-fifth aspect of the present disclosure, there is provided a system according to any of the twenty-second to twenty-fourth aspects, wherein the finely divided polyolefin particles comprise polyethylene.

[0112] According to a twenty-sixth aspect of the present disclosure, there is provided a system according to any one of the twenty-second to twenty-fifth aspects, wherein the system further comprises a second heat exchanger downstream of the first heat exchanger, wherein the second heat exchanger is configured to obtaining a second cooled gas stream.

[0113] According to a twenty-seventh aspect of the present disclosure, there is provided a system according to any one of the twenty-second to twenty-sixth aspects, characterized in that the bypass line exit is located upstream of the second heat exchanger, and the second gas stream is the first cooled gas stream.

[0114] According to a twenty-eighth aspect of the present disclosure, there is provided a system according to any one of the twenty-second to twenty-seventh aspects, characterized in that the system further comprises a compressor configured to compress the second cooled gas stream to form a compressed gas stream.

[0115] In accordance with the twenty-ninth aspect of the present disclosure, there is provided a system according to any one of the twenty-second to twenty-sixth aspects, characterized in that the bypass line outlet is located downstream of the second heat exchanger, and the second gas stream is the second cooled gas stream.

[0116] According to a thirtieth aspect of the present disclosure, there is provided a system according to a twenty-ninth aspect, characterized in that the system further comprises a compressor configured to compress the first cooled gas stream to form a compressed gas stream that is fed to a second heat exchanger.

[0117] According to the thirty-first aspect of the present disclosure, there is provided a system according to any of the twenty-second to thirtieth aspects, wherein the system further comprises a bypass line outlet variable valve to control the bypass flow rate.

[0118] According to the thirty-second aspect of the present disclosure, there is provided a system according to any one of the twenty-second to thirty-first aspects, characterized in that the inlet of the bypass line includes an intake extending into the vent line.

[0119] In accordance with the thirty-third aspect of the present disclosure, a system is provided in accordance with any of the twenty-second to thirty-second aspects, characterized in that the bypass line is configured to receive from about 5 wt. % to about 75 wt. % of the first gas flow.

[0120] According to a thirty-fourth aspect of the present disclosure, there is provided a system according to any of the twenty-second to thirty-third aspects, wherein the vent line comprises a substantially hemispherical bend.

[0121] According to the thirty-fifth aspect of the present disclosure, there is provided a system according to the thirty-fourth aspect, characterized in that the bypass line extends tangentially to the hemispherical bend.

[0122] According to a thirty-sixth aspect of the present disclosure, there is provided a system according to the thirty-fourth aspect, wherein the bypass line is at an angle of about 30 degrees to about 90 degrees from a line bisecting a substantially hemispherical bend.

[0123] In accordance with the thirty-seventh aspect of the present disclosure, a system is provided in accordance with any of the twenty-second to thirty-sixth aspects, characterized in that the bypass line is configured to preferentially remove up to about 80 wt. % entrained fine polyolefin particles into the exhaust line.

[0124] According to a thirty-eighth aspect of the present disclosure, there is provided a system according to any one of the twenty-second to thirty-seventh aspects, wherein the fine polyolefin particles have an average diameter of less than about 200 microns.

[0125] According to a thirty-ninth aspect of the present disclosure, there is provided a system according to any of the twenty-second to thirty-eighth aspects, wherein the fine polyolefin particles have an average diameter of less than about 150 microns.

[0126] According to the fortieth aspect of the present disclosure, there is provided a system according to any of the twenty-second to thirty-ninth aspects, wherein the fine polyolefin particles have an average diameter of less than about 10 microns.

[0127] According to the forty-first aspect of the present disclosure, there is provided a system according to any one of the twenty-second to fortieth aspects, characterized in that the bypass line has an internal diameter that is from about 10% to about 40% of the internal diameter of the vent line. .

[0128] According to the forty-second aspect of the present disclosure, there is provided a system according to any one of the twenty-second to forty-first aspects, wherein the bypass line inlet has an internal diameter that is from about 5% to about 50% greater than internal diameter of the bypass line.

[0129] According to a forty-third aspect of the present disclosure, there is provided a process for polymerizing olefins, comprising: contacting one or more olefins with a catalyst under polymerization conditions in a polymerization reactor to form a first gas stream containing solid fine particles and unreacted olefins; supplying the first gas stream to the exhaust line; preferentially removing a portion of the solid fine particles from the vent line to form a bypass stream containing a higher concentration of solid fine particles than is present in the first gas stream; supplying the bypass stream to a bypass line comprising a bypass line inlet and a bypass line outlet, the bypass line inlet being located upstream of the first heat exchanger and the bypass line outlet being located downstream of the first heat exchanger; supplying at least a portion of the first gas stream to the first heat exchanger, in which the first cooled gas stream is obtained; and combining the bypass stream and the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, wherein the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0130] According to a forty-fourth aspect of the present disclosure, there is provided a method according to the forty-third aspect, further comprising: supplying a first gas stream to a fine particle separator in fluid communication with a polymerization reactor and an exhaust line to separate a first portion of solid fine particles from unreacted olefins before the first gas stream is fed into the gas outlet line; and supplying the first portion of the solid fine particles to an eductor in fluid communication with the fine particle separator to move the first portion of the solid fine particles back to the polymerization reactor.

[0131] According to the forty-fifth aspect of the present disclosure, there is provided a method according to the forty-fourth aspect, characterized in that the eductor comprises: a first tubular body having a hollow interior and containing a first inlet and a first outlet spaced from the first inlet along a central axis , and a side wall surrounding the central axis and defining the mixing chamber; and a second tubular body having a hollow interior and comprising a second inlet and a second outlet spaced therefrom, wherein the second tubular body extends into the mixing chamber through a side wall of the first tubular body between the first inlet and the first outlet, the second inlet being oriented substantially perpendicularly axis of the first tubular body, wherein the second tubular body comprises a first bend less than 90° from the perpendicular to the first outlet before passing into the mixing chamber, and the second tubular body comprises a second bend less than 90° to the first outlet after passing into the mixing chamber.

[0132] According to a forty-sixth aspect of the present disclosure, there is provided a process according to any one of the forty-third to forty-fifth aspects, wherein the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen, and one or more paraffins.

[0133] According to the forty-seventh aspect of the present disclosure, there is provided a process according to any one of the forty-third to forty-sixth aspects, wherein the first gas stream contains one or more of pentane, isopentane, hexene, 1-hexene, ethylene , nitrogen and hydrogen.

[0134] According to a forty-eighth aspect of the present disclosure, there is provided a method according to any of the forty-third to forty-seventh aspects, wherein the finely divided polyolefin particles comprise polyethylene.

[0135] According to a forty-ninth aspect of the present disclosure, there is provided a method according to any one of the forty-third to forty-eighth aspects, further comprising supplying a first cooled gas stream to a second heat exchanger that produces a second cooled gas stream.

[0136] According to a fiftieth aspect of the present disclosure, there is provided a method according to any one of the forty-third to forty-ninth aspects, wherein the bypass line outlet is located upstream of the second heat exchanger, and the second gas stream is the first cooled gas flow.

[0137] In accordance with the fifty-first aspect of the present disclosure, there is provided a method according to the fiftieth aspect, further comprising supplying a second cooled gas stream to a compressor to form a compressed gas stream.

[0138] In accordance with the fifty-second aspect of the present disclosure, there is provided a method according to any one of the forty-third to forty-ninth aspects, wherein the bypass line outlet is located downstream of the second heat exchanger, and the second gas stream is the second cooled gas stream.

[0139] According to a fifty-third aspect of the present disclosure, there is provided a method according to the fifty-second aspect, further comprising supplying a first cooled gas stream to a compressor to form a compressed gas stream; and supplying the compressed gas stream to the second heat exchanger.

[0140] According to a fifty-fourth aspect of the present disclosure, there is provided a method according to any one of the forty-third to fifty-third aspects, further comprising adjusting a bypass line outlet valve to control the bypass flow rate.

[0141] According to a fifty-fifth aspect of the present disclosure, there is provided a method according to any one of the forty-third to fifty-fourth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration entrained fine polyolefin particles than is present in the first gas stream, includes the removal of about 5 wt. % to about 75 wt. % of the first gas flow.

[0142] According to a fifty-sixth aspect of the present disclosure, there is provided a method according to any one of the forty-third to fifty-fifth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the vent line to form a bypass stream containing a higher concentration entrained fine polyolefin particles than is present in the first gas stream results in a loss in cold performance of about 1% to about 20%.

[0143] According to a fifty-seventh aspect of the present disclosure, there is provided a method according to any one of the forty-third to fifty-sixth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the gas line to form a bypass stream containing a higher concentration entrained fine polyolefin particles than is present in the first gas stream results in a loss in cooling capacity of the first heat exchanger from about 1% to about 50%.

[0144] According to a fifty-eighth aspect of the present disclosure, there is provided a method according to any one of the forty-third to fifty-sixth aspects, wherein the step of preferentially removing a portion of the entrained fine polyolefin particles from the gas line to form a bypass stream containing a higher concentration entrained fine polyolefin particles than is present in the first gas stream results in a loss in cooling capacity of the first heat exchanger from about 5% to about 150%.

[0145] In accordance with the fifty-ninth aspect of the present disclosure, a method is provided in accordance with any of the forty-third to fifty-eighth aspects, characterized in that the bypass stream contains up to about 80 wt. % entrained fine polyolefin particles in the first gas stream.

[0146] According to a sixtieth aspect of the present disclosure, there is provided a method according to any of the forty-third to fifty-ninth aspects, wherein the fine polyolefin particles have an average diameter of less than about 200 microns.

[0147] According to the sixty-first aspect of the present disclosure, there is provided a method according to any of the forty-third to sixtieth aspects, wherein the fine polyolefin particles have an average diameter of less than about 150 microns.

[0148] According to the sixty-second aspect of the present disclosure, there is provided a method according to any of the forty-third to sixty-first aspects, wherein the fine polyolefin particles have an average diameter of less than about 10 microns.

[0149] According to a sixty-third aspect of the present disclosure, an olefin polymerization system is provided, comprising: a polymerization reactor for contacting one or more olefins with a catalyst under polymerization conditions to form a first gas stream containing solid fine particles and unreacted olefins; a gas outlet line configured to receive the first gas stream; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a cooled gas stream; a bypass line configured to preferentially remove a portion of the solid fine particles from the gas outlet line to form a bypass stream containing a higher concentration of solid fine particles, the bypass line comprising an inlet and an outlet, the inlet being located upstream of the first heat exchanger, the outlet located downstream of the first heat exchanger, and wherein the bypass line is configured such that the bypass stream is combined with the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and the temperature of the combined gas stream is below the dew point of the combined gas stream.

[0150] According to a sixty-fourth aspect of the present disclosure, there is provided a system according to the sixty-third aspect, characterized in that the system further comprises: a fine particle separator in fluid communication with the polymerization reactor for separating solid fine particles from unreacted olefins; and an eductor in fluid communication with the fine particle separator for moving the solid fine particles back to the polymerization reactor.

[0151] According to the sixty-fifth aspect of the present disclosure, there is provided a system according to the sixty-fourth aspect, characterized in that the eductor comprises: a first tubular body having a hollow interior and containing a first inlet and a first outlet spaced from the first inlet along a central axis , and a side wall surrounding the central axis and defining the mixing chamber; and a second tubular body having a hollow interior and comprising a second inlet and a second outlet spaced therefrom, wherein the second tubular body extends into the mixing chamber through a side wall of the first tubular body between the first inlet and the first outlet, the second inlet being oriented substantially perpendicularly axis of the first tubular body, wherein the second tubular body comprises a first bend less than 90° from the perpendicular to the first outlet before passing into the mixing chamber, and the second tubular body comprises a second bend less than 90° to the first outlet after passing into the mixing chamber.

[0152] According to the sixty-sixth aspect of the present disclosure, there is provided a system according to any one of the sixty-third to sixty-fifth aspects, wherein the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen, and one or more paraffins.

[0153] According to the sixty-seventh aspect of the present disclosure, there is provided a system according to any of the sixty-third to sixty-sixth aspects, characterized in that the first gas stream contains one or more of pentane, isopentane, hexene, 1-hexene, ethylene , nitrogen and hydrogen.

[0154] According to the sixty-eighth aspect of the present disclosure, there is provided a system according to any of the sixty-third to sixty-seventh aspects, wherein the finely divided polyolefin particles comprise polyethylene.

[0155] According to a sixty-ninth aspect of the present disclosure, there is provided a system according to any one of the sixty-third to sixty-eighth aspects, wherein the system further comprises a second heat exchanger downstream of the first heat exchanger, wherein the second heat exchanger is configured to obtaining a second cooled gas stream.

[0156] According to the seventieth aspect of the present disclosure, there is provided a system according to any one of the sixty-third through sixty-ninth aspects, characterized in that the bypass line outlet is located upstream of the second heat exchanger, and the second gas stream is the first cooled gas flow.

[0157] According to the seventy-first aspect of the present disclosure, there is provided a system according to the seventieth aspect, characterized in that the system further comprises a compressor configured to compress the second cooled gas stream to form a compressed gas stream.

[0158] In accordance with the seventy-second aspect of the present disclosure, there is provided a system according to any one of the sixty-third through sixty-ninth aspects, characterized in that the bypass line outlet is located downstream of the second heat exchanger, and the second gas stream is the second cooled gas stream.

[0159] According to the seventy-third aspect of the present disclosure, there is provided a system according to the seventy-second aspect, characterized in that the system further comprises a compressor configured to compress the first cooled gas stream to form a compressed gas stream that is fed to a second heat exchanger.

[0160] According to the seventy-fourth aspect of the present disclosure, there is provided a system according to any one of the sixty-third through seventy-three aspects, wherein the system further comprises a bypass line outlet variable valve for controlling the bypass flow rate.

[0161] According to the seventy-fifth aspect of the present disclosure, there is provided a system according to any of the sixty-third to seventy-fourth aspects, characterized in that the inlet of the bypass line includes an intake extending into the vent line.

[0162] In accordance with the seventy-sixth aspect of the present disclosure, a system is provided in accordance with any of the sixty-third to seventy-fifth aspects, characterized in that the bypass line is configured to receive from about 5 wt. % to about 50 wt. % of the first gas flow.

[0163] According to the seventy-seventh aspect of the present disclosure, there is provided a system according to any one of the sixty-third to seventy-sixth aspects, wherein the vent line comprises a substantially hemispherical bend.

[0164] According to the seventy-eighth aspect of the present disclosure, there is provided a system according to the seventy-seventh aspect, characterized in that the bypass line is tangential to the hemispherical bend.

[0165] According to a seventy-ninth aspect of the present disclosure, there is provided a system according to the seventy-seventh aspect, wherein the bypass line is at an angle of about 30 degrees to about 90 degrees from a line bisecting a substantially hemispherical bend.

[0166] In accordance with the eightieth aspect of the present disclosure, a system is provided in accordance with any of the sixty-third to seventy-ninth aspects, characterized in that the bypass line is configured to preferentially remove up to about 80 wt. % fine solids into the exhaust line.

[0167] According to the eighty-first aspect of the present disclosure, there is provided a system according to any of the sixty-third through eightieth aspects, wherein the fine polyolefin particles have an average diameter of less than about 200 microns.

[0168] According to the eighty-second aspect of the present disclosure, there is provided a system according to any of the sixty-third through eighty-first aspects, wherein the fine polyolefin particles have an average diameter of less than about 150 microns.

[0169] According to the eighty-third aspect of the present disclosure, there is provided a system according to any of the sixty-third to eighty-second aspects, wherein the finely divided polyolefin particles have an average diameter of less than about 10 microns.

[0170] According to an eighty-fourth aspect of the present disclosure, there is provided a system according to any one of aspects sixty-three to eighty-three, wherein the bypass line has an inside diameter that is from about 10% to about 40% of the inside diameter of the vent line. lines.

Claims (33)

1. A system for reducing the fouling rate of a heat exchanger, comprising: an exhaust line configured to pass the first gas stream containing gas and entrained fine polyolefin particles; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a first cooled gas stream; and a bypass line configured to remove a portion of the entrained fine polyolefin particles from the exhaust line to form a bypass stream containing a higher concentration of entrained fine polyolefin particles than is present in the first gas stream, the bypass line comprising a bypass line inlet and a bypass line outlet, wherein the inlet of the bypass line is located upstream of the first heat exchanger, wherein the bypass line outlet is located downstream of the first heat exchanger, and wherein the bypass line is configured such that the bypass stream is combined with the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and wherein the temperature of the combined gas stream is below the dew point of the combined gas stream. 2. The system of claim. 1, characterized in that the first gas stream contains one or more of unreacted olefins, nitrogen, hydrogen and one or more paraffins. 3. The system according to claim. 1, characterized in that it further comprises a second heat exchanger downstream of the first heat exchanger, and the second heat exchanger is configured to receive a second cooled gas stream. 4. The system according to claim 3, characterized in that the bypass line outlet is located upstream of the second heat exchanger, and the second gas stream is the first cooled gas stream. 5. The system according to claim 1, characterized in that the system further comprises a compressor configured to compress the second cooled gas stream to form a compressed gas stream. 6. The system of claim. 1, characterized in that the output of the bypass line is located downstream of the second heat exchanger, and while the second gas stream is a second cooled gas stream. 7. The system according to claim 6, characterized in that the system further comprises a compressor configured to compress the first cooled gas stream to form a compressed gas stream that is fed to the second heat exchanger. 8. The system according to claim. 1, characterized in that the system further comprises an adjustable valve at the outlet of the bypass line to control the flow rate of the bypass flow. 9. The system according to claim 1, characterized in that the inlet of the bypass line contains an intake that extends into the gas outlet line. 10. The system according to claim. 1, characterized in that the bypass line is configured to receive from about 5 wt. % to about 75 wt. % of the first gas flow. 11. The system according to claim. 1, characterized in that the vent line contains an essentially hemispherical bend. 12. The system according to claim 11, characterized in that the bypass line runs tangentially to the hemispherical bend. 13. The system of claim. 11, characterized in that the bypass line is at an angle of from about 30 degrees to about 90 degrees from the line bisecting a substantially hemispherical bend. 14. The system according to p. 1, characterized in that the bypass line is made with the possibility of preferential removal of up to about 80 wt. % entrained fine polyolefin particles into the exhaust line. 15. The system of claim. 1, characterized in that the bypass line has an internal diameter that is from about 10% to about 40% of the internal diameter of the exhaust line. 16. The system of claim. 1, characterized in that the inlet of the bypass line has an internal diameter that is from about 5% to about 50% larger than the internal diameter of the bypass line. 17. An olefin polymerization system, comprising: a polymerization reactor for contacting one or more olefins with a catalyst under polymerization conditions to form a first gas stream containing solid fine particles and unreacted olefins; a gas outlet line configured to receive the first gas stream; a first heat exchanger configured to receive at least a portion of the first gas stream and obtain a cooled gas stream; a bypass line configured to remove part of the solid fine particles from the gas outlet line to form a bypass stream containing a higher concentration of solid fine particles, and the bypass line contains an inlet and an outlet, wherein the inlet is located upstream of the first heat exchanger, wherein the outlet is located downstream of the first heat exchanger, and wherein the bypass line is configured such that the bypass stream is combined with the second gas stream at the outlet of the bypass line to form a combined gas stream containing one or more olefins or paraffins, and wherein the temperature of the combined gas stream is below the dew point of the combined gas stream. 18. The system of claim 17, further comprising a second heat exchanger downstream of the first heat exchanger, wherein the second heat exchanger is configured to provide a second cooled gas stream. 19. The system according to claim 18, characterized in that the bypass line outlet is located upstream of the second heat exchanger, while the second gas stream is the first cooled gas stream, and the system optionally further comprises a compressor configured to compress the second cooled gas stream to form a compressed gas stream. 20. The system according to claim 18, characterized in that the bypass line outlet is located downstream of the second heat exchanger, while the second gas stream is a second cooled gas stream, and the system optionally further comprises a compressor configured to compress the first cooled gas stream to form a compressed gas stream, which is fed into the second heat exchanger.

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