Device for detecting initial crust in gas phase reactor

Abstract

The invention relates to a method for detecting initial crust in a polyolefin gas phase reactor. The method may include flowing one or more monomer gases through a first tube through a reactor wall, flowing one or more monomer gases through a second tube through the reactor wall, where the first tube is located within the second tube, and measuring a differential pressure of the monomer gases flowing through the first tube and the second tube. Based on the measured differential pressure, initial skinning within the reactor may be detected, and one or more reset measures may be employed to control or reverse the skinning.

Description

References to Cross-Related Applications

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 373,109, filed on August 22, 2022, entitled “Device for Detecting Initial Scaling in a Gas Phase Reactor,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] Embodiments of the present invention generally relate to gas phase polymerization. More specifically, embodiments of the present invention relate to an apparatus for detecting incipient sheeting in a polyolefin gas phase reactor. Background Art

[0003] If the skin grows large enough, skin formation in a gas phase reactor can cause reactor shutdown. Existing skin detection methods have used temperature monitoring and / or nuclear instrumentation at the plate level to detect the presence of skin, polymer lumps, or other large solid polymer clusters. However, these known methods fail to detect the problem until the solid polymer clusters grow too large to mitigate and prevent shutdown.

[0004] Therefore, there remains a need for new apparatus and methods for polymer agglomeration detection within gas phase reactors.

[0005] Some references that may be of interest in this regard include: U.S. Patent Nos. 3,779,712; 4,532,311; 7,985,811 and 7,634,937; and EP0366823, EP1082351, EP1082350, EP1106984, EP2101908, and EP0233787. Summary of the invention SUMMARY OF THE INVENTION

[0006] Provided herein are methods and apparatus for olefin polymerization in a gas phase reactor and for detecting incipient skinning in a gas phase reactor. Further provided are methods for retrofitting a gas phase polymerization reactor using slurry injection.

[0007] In one embodiment, the method for detecting initial crusting may include allowing one or more fluids to flow through a first tube protruding through a reactor wall, and measuring the pressure difference between a first point and a second point along the tube or upstream of the tube (relative to the direction of fluid flow) of the fluid flowing through the first tube. The tube preferably penetrates the reactor wall in a substantially horizontal orientation (e.g., substantially perpendicular to the reactor wall), and has an inner diameter less than or equal to 1 inch (2.54 cm), such as less than or equal to 0.5 inches, and is arranged at a certain height above the distributor plate in the reactor along the wall. Based on the measured pressure difference, initial crusting in the reactor can be detected, and one or more remedial measures can be used to control or reverse the crusting to avoid shutdown. Optionally, the first tube can be arranged in a second tube, the inner diameter of the second tube is greater than the outer diameter of the first tube, and when viewed along a positive cross-section, the two tubes are substantially concentric so that an annular space is defined between the first tube and the second tube.

[0008] In another embodiment, a process for olefin polymerization in a gas phase reactor may include injecting a catalyst mixture into the gas phase reactor via one or more catalyst injectors, each catalyst injector substantially horizontally penetrating the reactor wall at a first height within the reactor above a distributor plate within the reactor, wherein each catalyst injector comprises a first tube disposed within a second, larger tube, thereby forming an annular space therebetween, and further wherein the catalyst mixture (comprising catalyst particles and a carrier fluid) flows through the first tube of the catalyst injector and an additional fluid (e.g., monomer gas, ICA, and / or purge gas) flows through the second, larger tube of the catalyst injector. The carrier fluid may comprise a solvent, such as mineral oil, hexane, or other hydrocarbon liquid (e.g., for slurrying the catalyst mixture), and / or a carrier gas, such as an inert condensing agent (ICA), a purge gas, or other hydrocarbon or inert gas; the additional fluid may be the same or different from the fluid flowing through the first tube (and comprising one or more of ICA, purge gas, monomer gas, or other hydrocarbon or inert gas), noting that the carrier fluid should be inert, while the additional fluid is preferably inert, but not necessarily inert. In addition, one or more monomer gases can be provided to the reactor (optionally, the one or more monomer gases can be injected through at least one monomer injector, which penetrates the reactor wall at the same height as the first height or at a second height different from the first height within the reactor). The one or more monomer gases can be polymerized in the reactor in the presence of a catalyst to form finely divided solid polymer particles; and the pressure difference and / or flow rate in the first and / or second tubes of each of the one or more catalyst injectors can be measured (for example, the measurement can be made along the tubes or upstream of the tubes). In addition or alternatively, the pressure difference and / or flow rate in the monomer injector (if used) can be measured (again along the monomer injector or upstream of the monomer injector). A significant reduction in the pressure difference at any of the above-mentioned tubes and / or injectors indicates the presence of initial skinning within the reactor. Therefore, based at least in part on the detected reduction in the measured pressure difference and / or flow rate values, one or more remedial measures can be taken to control or reverse skinning to avoid shutdown.

[0009] In another embodiment, the method for refurbishing a gas phase polymerization reactor using slurry injection may include adding one or more devices for injecting one or more fluids into the reactor, wherein each device has at least one flow path passing therethrough and one or more instruments for measuring pressure variation pulses (burst) passing through the flow path. The one or more devices are located below the catalyst injection nozzle for slurry injection and above the distribution plate in the reactor. Hydrocarbon liquid or gas can flow through each of the one or more added devices, and intermittent pressure drops can be detected via each device to detect crust formation in the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order that the above-listed features of the present invention may be understood in detail, a more specific description of the present invention briefly outlined above may be obtained by reference to some of the embodiments shown in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the present invention and are therefore not to be considered as limiting the scope of the present invention, as the present invention may be implemented with other equally effective embodiments. It should be emphasized that the drawings are not necessarily drawn to scale, and for the sake of clarity and / or simplicity, certain features and certain views of the drawings may be shown in scale or in schematic enlargement.

[0011] Figure 1 Depicted is an exemplary apparatus for detecting incipient skinning within a polymer reactor according to one or more embodiments described herein.

[0012] Figure 2 A schematic diagram of an exemplary gas phase polymerization reactor is depicted.

[0013] Figure 3 Describes the past Figure 2 An illustrative partial cross-sectional view of the reactor of line 3-3. DETAILED DESCRIPTION OF THE INVENTION

[0014] It should be understood that the following disclosure describes several exemplary embodiments for realizing different features, structures or functions of the present invention. The exemplary embodiments of components, arrangements and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided as examples only and are not intended to limit the scope of the present invention. In addition, the present disclosure may repeat reference numbers and / or letters in various embodiments and in the accompanying drawings provided herein. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between various embodiments and / or configurations. In addition, forming a first feature above or on a second feature in the subsequent description may include an embodiment in which the first and second features are formed as direct contacts, and may also include an embodiment in which additional features may be formed between the first and second features so that the first and second features are not in direct contact. Finally, the embodiments provided below may be combined in any manner, that is, any element from one embodiment may be used in any other exemplary embodiment without departing from the scope of the disclosure.

[0015] In addition, certain terms are used in the following description and claims to refer to specific components. As will be appreciated by those skilled in the art, various entities may refer to the same component by different names, and therefore, unless specifically defined otherwise herein, the naming conventions of the elements described herein are not intended to limit the scope of the present invention. Furthermore, the naming conventions used herein are not intended to distinguish between components that differ in name but function.

[0016] In the following discussion and in the claims, the terms "comprising" and "including" are used in an open-ended manner, and thus should be interpreted to mean "including but not limited to." The phrase "consisting essentially of" means that the described / claimed composition does not contain more than 5% of any other component that would materially alter its property, and in any case, does not contain any other component to a level greater than 3 weight percent.

[0017] The term "or" is intended to cover both the exclusive and inclusive case, ie, "A or B" is intended to be synonymous with "at least one of A and B" unless the context clearly indicates otherwise.

[0018] The indefinite articles "a" and "an" refer to both the singular (i.e., "a / an") and plural referents (i.e., one or more) unless the context clearly dictates otherwise. For example, embodiments using "olefin" include embodiments in which one, two, or more olefins are used, unless otherwise specified or the context clearly dictates that only one olefin is used.

[0019] The term "wt%" means weight percent, "vol%" means volume percent, "mole%" means mole percent, "ppm" means parts per million, "ppm wt" and "wppm" are used interchangeably and refer to parts per million by weight. Unless otherwise indicated, all concentrations are expressed based on the total amount of the composition in question.

[0020] The term "α-olefin" refers to any linear or branched compound of carbon and hydrogen having at least one double bond between the α and β carbon atoms. For purposes of this specification and the claims thereto, when a polymer or copolymer is referred to as comprising an α-olefin, such as a poly-α-olefin, the α-olefin present in such a polymer or copolymer is the polymerized form of the α-olefin.

[0021] The term "fluid communication" means that fluid can be transferred from a first component to a second component directly or via at least a third component. The term "inlet" refers to the point at which a fluid enters a component, and the term "outlet" refers to the point at which a fluid leaves a component.

[0022] Each of the attached claims defines an independent invention, which, for the purpose of preventing infringement, should be deemed to include equivalents to the various elements or limitations specified in these claims. Depending on the context, all references to the "invention" may refer to only certain specific embodiments in some cases. In other cases, it will be recognized that references to the "invention" will refer to one or more (but not necessarily all) of the subject matter described in the claims. Each of the present inventions will now be described in more detail below, including specific embodiments, versions and examples, but the present invention is not limited to these embodiments, versions or examples, and they are included to enable those of ordinary skill in the art to make and use the present invention when combining the information in this disclosure with publicly available information and technology.

[0023] Various embodiments of the present disclosure include methods for detecting initial skinning in a gas phase polymerization reactor, such as a fluidized bed polymerization reactor, wherein a fluidized bed is established by directing gas through a distribution plate disposed at the bottom of the reactor so that the gas flows upward through a large number of particles that generally contain catalyst and growing polymer particles. The gas flow and distribution are based on the known principles for establishing and maintaining a fluidized bed of particles in a reactor. However, as previously described, these particles can agglomerate into increasingly larger pieces or "sheets" under conditions in the reactor-a phenomenon known as "sheeting". The method of the present invention includes transmitting one or more fluids (e.g., catalyst particles in monomer gas, carrier gas and / or solution, or a combination thereof) to the reactor via a tube that substantially horizontally penetrates the reactor wall and enters the interior of the reactor, preferably at a certain height along the reactor wall so that the tube extends into the fluidized bed region in the reactor. The pressure drop and / or flow rate of the fluid (e.g., the pressure drop between the first point and the second point along the tube) are continuously measured on a portion of the tube, and initial skinning is detected based on the measured pressure drop (or flow rate). In particular, it is believed that any polymer agglomerates that begin to form in the fluidized bed zone will move rapidly around that zone and, soon after formation, will strike or otherwise contact the tube, causing flow to be interrupted.

[0024] Advantageously, if the tube diameter is small enough, rapid impacts and / or small agglomerates will substantially interrupt the flow of fluid through the tube, resulting in a large drop in the measured pressure drop (or flow rate) value, so that when such a drop is detected, the presence of incipient skinning can be easily inferred. Thus, the present method provides an advantageous early warning of skinning, enabling corrective measures to be taken to mitigate or reverse the skinning problem, thereby avoiding reactor shutdown.

[0025] By employing a tube having a sufficiently small inner diameter (e.g., 1 inch (2.54 cm) or less, preferably 0.5 inch (1.27 cm) or less, most preferably 0.25 inch (0.635 cm) or less, e.g., in the range of 0.1 to 0.25, 0.5, 0.75, or 1.0 inches) and penetrating the reactor in a substantially horizontal orientation (i.e., perpendicular to the reactor wall and parallel to the distributor plate), the present method provides significant advantages over other previously disclosed methods of detecting flakes, which rely on vertical conduits, transducers, or other devices disposed through the distributor plate, where a large amount of flakes would be required prior to initial detection at or near the distributor plate. See, e.g., EP2101908 and EP0233787. The advantages of the present method can be further enhanced via certain specific configurations; for example, a device comprising two tubes (an inner tube and an outer tube oriented concentrically such that the inner tube is disposed within the outer tube, forming an annular space therebetween) can be used. In addition, the inner tube can be flexible while the outer tube or support tube is rigid; and the inner tube can protrude an additional portion (e.g., between 1 / 32 inch and 5 inches) farther into the reactor than the outer tube, so that the flexible end point of the inner tube can be struck by initially forming agglomerates in a manner that significantly inhibits flow out of the tube, thereby enabling detection of a significant reduction in the measured pressure drop (or flow rate) through the inner tube.

[0026] Furthermore, the present method can advantageously use existing equipment, such as catalyst feeders or other tubes for conveying gases into the reactor via essentially horizontal tubes penetrating the reactor wall; however, in addition or alternatively, the method can be employed using a dedicated tube (or an arrangement comprising an inner tube and an outer tube) positioned along the reactor wall and penetrating the reactor wall horizontally at a short distance above (or almost adjacent to) the distribution plate in order to detect skinning at the plate level as early as possible.

[0027] As noted, although the process can be employed using a single tube protruding horizontally into the reactor, certain embodiments employ a configuration with an inner tube and an outer tube as just mentioned. Such a configuration is discussed in more detail below in conjunction with the accompanying drawings, as are gas phase polymerization reactors and processes.

[0028] Figure 1An illustrative apparatus 100 for detecting incipient skinning inside a gas phase polymerization reactor is depicted, according to one or more embodiments. Apparatus 100 may include an injection tube or first tube 120 disposed within a support tube or second tube 110; injection tube 120 and support tube 110 are preferably concentric; injection tube 120 has an outer diameter (OD) that is smaller than an inner diameter (ID) of the surrounding support tube 110, thereby forming an annular space therebetween. The first tube and second tube are preferably oriented substantially horizontally (e.g., substantially perpendicular to the reactor wall) and protrude into reactor 200 above a distribution plate 210 located near the bottom of the reactor, such as Figure 2 As shown. The device 100 can be located at any suitable height above the distribution plate 210, and includes a height such that the device 100 is nearly adjacent to the distribution plate (while still extending substantially horizontally into the reactor), for example, at a distance above the distribution plate 210 of about 0.2 ft, 0.5 ft, 0.7 ft, 0.9 ft, 1 ft, 2 ft, 3 ft, 4 ft, 5 ft, or 6 ft to about 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 ft (with a range from any of the foregoing lower limits to any of the foregoing upper limits, provided that the upper limits are greater than the lower limits). It should be understood that the size of the reactor will affect the height above the distribution plate 210 at which the device 100 is disposed; in any case, the device 100 is preferably disposed at a height along the reactor wall 205 such that the device 100 protrudes into the fluidized bed region of the reactor 200. The support tube 110 can be fixed to the reactor wall 205, and the injection tube 120 can be removed from the support tube 110. The smaller injection tube 120 can be inserted into the larger surrounding support tube 110 through a packing gland. The packing gland can be used to provide a fluid tight seal between the surrounding of the injection tube 120 and the support tube 110.

[0029] Optionally, as previously described, the inner tube may optionally be at least partially flexible. On the other hand, the outer tube or support tube is preferably substantially rigid. More specifically, the size of the surrounding outer tube 110 can be suitable for withstanding the forces of the fluidized bed and the forces of the falling crust within the reactor 200 (and made of such a material). Therefore, the surrounding outer tube 110 can serve as a support tube for the inner injection tube 120 located therein. The surrounding outer tube 110 or simply "support tube" is typically a thick wall tube and, as described above, has an inner diameter that is greater than the outer diameter of the inner tube 120. The inner diameter of the outer tube 110 can be in the range of about 1 / 4 inch to about 5 inches (0.64 cm to 12.7 cm), preferably in the range of about 1 / 2 inch to about 3 inches (1.3 cm to 7.6 cm), and more preferably in the range of about 3 / 4 inch to about 2 inches (1.9 cm to 5 cm), and ranges from any of the foregoing lower limits to any of the foregoing upper limits are also contemplated, provided that the upper limit is greater than the lower limit (e.g., about 1 / 2 inch to about 2 inches (about 1.3 cm to about 5 cm). The length of the surrounding outer tube 110 can be in the range of about 30" to 50". The tube 110 can extend into the reactor 200, or can terminate flush with the inner surface of the reactor wall 205. The end of the tube 110 can be cut flat and perpendicular to the axis of the tube 110, or it can be tapered at an angle ranging from about 10 degrees to 80 degrees. The end of the support tube 110 can also be polished or coated with an antistatic or anti-fouling material.

[0030] The smaller diameter or inner tube 120 may have an inner diameter of less than about 1", or less than about 0.5", more preferably less than about 0.25", such as less than 0.20" or less than 0.1875", and in configurations where an outer or support tube 110 is used, the inner diameter of the inner tube 120 is of course smaller than its outer diameter, and the outer diameter of the inner tube 120 is in turn smaller than the inner diameter of the support tube 110. The inner or injection tube 120 may extend through the compressed V-shaped packing into the reactor 200 and into the fluidized bed a distance of about 0.1 inch to 10 feet (0.25 cm to 3.1 m), preferably about 1 inch to 6 ft (2.5 cm to 1.8 m), more preferably about 2 inches to 5 feet (5 cm to 1.5 m). Typically, the insertion depth depends on the diameter of the reactor 200, and typically extends from about 1 / 20 to 1 / 2 of the reactor diameter, preferably about 1 / 10 to 1 / 2, more preferably about 1 / 5 to 1 / 3 of the reactor diameter.

[0031] The end (e.g., "first end") 120a of the injection tube 120 can be flush with the end (e.g., "first end") 110a of the support tube 110. The end 120a of the inner tube 120 can also extend beyond the end 110a of the support tube 110. For example, the end 120a of the inner tube 120 can extend from the end 110a of the outer tube 110 by about 1 / 6", 1 / 8", 3 / 16", 0.25", or 1 / 2", such as within a range from a lower limit of any one of about 1 / 16, 3 / 16, 1 / 4, or 1 / 2 inches to an upper limit of any one of about 1 / 2, 3 / 4, 1, 2, 3, 4, or 5 inches, provided that the upper limit is greater than the lower limit. Such a configuration can advantageously expose the ends of the tubes to skinning swirling within the fluidized bed of the reactor, making it easier to record flow disruptions that result in reduced pressure drop (or flow rate) measurements across the inner tube, thereby better signaling initial skinning.

[0032] The end 120a of the injection tube 120 may be cut perpendicular to its axis to produce a tapered end or point with an angle ranging from 0 to 90 degrees, preferably ranging from about 0 to 60 degrees or 10 to 80 degrees. The tube 120 may be coated with an antifouling or antistatic compound.

[0033] Still reference Figure 1, the device 100 may also include one or more flow meters (two 130, 135 are shown) or other instruments for measuring, warning and / or detecting fluctuations in flow and / or pressure through the tubes 110, 120. For example, such an instrument may be adapted to measure a pressure drop across the instrument (such that a pressure drop is measured from a first point (the upstream end of the instrument relative to fluid flow through the tube) to a second point (the downstream end of the instrument)). More generally, it is convenient to make pressure drop measurements using a first point and a second point that are reasonably close to each other along the tube; or on either side of a device, such as the instrument just mentioned; so long as the distance and / or instrument over which the pressure drop is measured is large enough so that a measurable pressure drop can be obtained at the measurement location. One of ordinary skill will be well versed in selecting a means for determining a measurable pressure drop along the tube, but it should be noted that distances such as 0.5 ft, 1 ft, 1.5 ft, 2 ft, 5 ft or more may be appropriate when a specific device for measuring the pressure drop is not employed. Likewise, the pressure drop may be measured at a specific fitting, such as a pick-up block or other fitting. Most generally, for the practice of the methods described herein, any distance for pressure drop measurement will be suitable, as long as the distance is consistent, so that the measured pressure drop change (e.g., decrease) caused by the interaction of, for example, the crust of the tube facing the reactor opening can be detected, and as long as the distance is large enough, so that considering the tube (including any accessories) measuring the pressure drop, a measurable pressure drop can be obtained without erroneously changing the noise in the measurement. The pressure drop can be measured at a first point and a second point along the tube or upstream of the tube (e.g., in an adjacent pipe, flange, fitting, etc.). When flow meters 130, 135 are used for this purpose, instruments 130, 135 can be located upstream of tubes 110, 120, such as in an adjacent pipe or connecting flange on the inlet of tubes 110, 120. Suitable instruments 130, 135 include any conventional, fast trending tools that can be monitored using conventional instruments or programmable logic control operations. Such suitable instruments 130, 135 should be able to provide high-speed data collection to detect instantaneous interruptions of flow from passing crusts in real time. This information can be displayed in a control center, used to monitor spikes in real time or form the basis of a set of alarms.

[0034] Likewise, flow velocity may be measured and / or determined along or upstream of the tube (e.g., flow velocity may be derived from the pressure drop measurements described above using the area of ​​the cross-sectional profile of the tube or other conduit along which the pressure drop is measured, as will be appreciated by those skilled in the art). Likewise, a decrease in the measured and / or determined flow velocity value will also be used to indicate skinning, as will a decrease in the measured pressure drop value.

[0035] In addition, it is expected that measuring the flow rate or pressure difference in the outer tube or upstream of the outer tube can have an indication value similar to measuring the flow rate or pressure difference in the inner tube or upstream of the inner tube. Therefore, some embodiments may include measuring the flow rate or pressure difference in either or both of the inner and outer tubes; and in particular, some of these embodiments include measuring the flow rate or pressure difference in both the inner and outer tubes.

[0036] As already mentioned, a reduction in pressure drop and / or flow rate measured at a tube (such as those described herein) can be an excellent indicator of sheeting in the reactor. During polymerization, small clumps or skins of material (e.g., polymer being formed) contacting the outlet or outlet end of a tube (e.g., inner tube 120, outer tube 110 of apparatus 100, or both) can cause intermittent changes in flow rate and / or pressure drop (also referred to as differential pressure, ΔP, or DP for short) through the tube. Short pulses of reduced flow and / or pressure drop through the tube can indicate that skinning has occurred within reactor 200. By "short pulses" is meant a small clump of material or skin (e.g., polymer being formed) contacting the outlet or outlet end of a tube (e.g., inner tube 120, outer tube 110, or both of apparatus 100). Figure 1 The flow rate or pressure drop or both of the tubes 110 and / or 120 of the device 100 shown in the figure changes (i.e., decreases) by at least about 30%, about 40%, about 50%, about 65%, about 75%, or about 90% or more within a time range of about 1 hour or less, 30 minutes or less, 15 minutes or less, or 1 minute or less. The time range can also be from a lower limit of about 1, 30, or 60 seconds to an upper limit of about 3, 5, or 30 minutes. The operator and / or program can also define a threshold value or a predetermined amount of acceptable deviation for such a short pulse, so that when the threshold value and / or predetermined amount is exceeded (e.g., the DP and / or flow rate decreases by more than 50% within a time period from a lower limit of 1 second to an upper limit of 30 minutes, such as 5 seconds or 30 seconds, etc.), it can be inferred that initial skinning has been detected and one or more steps to reduce the degree of skinning and prevent reactor shutdown can be initiated. The reduction is a measured value relative to the operation before the reduction begins; for example, this may be a steady-state operating condition, or it may be an expected operating value (for example, following a known ramp curve during reactor startup, restart, etc., a continuously increasing or decreasing pressure differential consistent with the particular startup operation employed may be measured, and then a sudden reduction is detected (or, where a gradual reduction is expected, a sudden, larger than expected reduction is detected), indicating the potential onset of crusting).

[0037] Skinning mitigation (i.e., remedial measures) can include any suitable action that is expected to reduce or prevent skinning. For example, the reactor temperature can be reduced. The monomer feed rate and / or ICA feed rate (e.g., other hydrocarbons, and particularly alkanes, such as one or more of propane, butane, pentane, and including normal isomers and isomers of the foregoing substances) can be reduced. The concentration / partial pressure of hydrocarbons can be reduced, for example, by discharging a portion of the reactor overhead stream and / or recovery unit to a flare. The monomer partial pressure (M-PP) can be adjusted (increase M-PP if productivity is too low, reduce M-PP if productivity is too high). The catalyst flow rate / production rate can be reduced. The reactor can be converted to a different grade requiring different operating conditions, which is just commensurate with or incorporated into any of the aforementioned corrective measures (i.e., the target melt index and / or density of the polymer being produced in the reactor can be changed). The height of the fluidized bed (containing a plurality of catalyst particles and growing polymer particles, as previously described) can be increased by, for example, increasing the monomer feed rate and / or the catalyst feed rate and changing the polymer discharge rate from the reactor to the product discharge system. Water or other antistatic agents can be added to the reactor. In any of the foregoing remedial measures, the term "decrease" or "increase" refers to one or more incremental adjustments, which can range from 1% to 20% of the rate or value of the adjusted parameter; 3% to 15%; or 5% to 10% (relative to the value of such parameter before the initial skinning (as indicated by the measured DP reduction and / or flow reduction)) is detected. These adjustments can also be within the range of a lower limit of about 1%, 3% or 5% to an upper limit of about 10%, 30%, 50%, 80% or 99%.

[0038] In a particular embodiment, the reactor temperature can be reduced to alleviate the viscosity of the polymer (considering that higher temperatures lead to higher viscosity, and therefore higher likelihood of skinning). Reducing the reactor temperature increases the temperature difference between the polymer melt temperature and the reactor temperature. It is this temperature difference that affects the viscosity of the polymer. Reducing the melt index and / or increasing the density also increases the melting point of the polymer, which will increase this temperature difference. Reducing the partial pressure of hydrocarbons (especially heavy hydrocarbons) reduces the melting point depression, thereby increasing the melting point (thereby again increasing the difference between the reactor temperature and the melt temperature). These are several examples of manipulating the temperature difference between the reactor temperature and the melt temperature of the polymer. Additional details of these techniques are set forth in U.S. Patent No. 7,774,178, which is incorporated herein by reference.

[0039] Reference now Figure 2 and 3 , Figure 2 is a front view of a gas phase polymerization reactor 200, and Figure 3 Shows the Figure 23-3 of the reactor 200, any number of devices 100 may be located around the reactor 200. For example, the reactor 200 may have one, two, three, four, five, six, seven, eight, or more devices 100 ( Figure 3 200). Seven (7) devices 100a-100g are shown in FIG. 200 . Devices 100 may be used as injection nozzles for any one or more of reaction gases, catalysts, recycle gases, condensing agents, carrier or purge fluids (e.g., carrier or purge gases), and any other fluids (and in particular any gases) to be injected into polymerization reactor 200. For example, device 100 may be used to provide catalyst particles in a carrier fluid, e.g., catalyst particles in a carrier gas such as nitrogen, and / or an induced condensing agent (ICA), etc. Similarly, device 100 may be used to provide one or more of a monomer feed gas, an ICA, and a purge gas (e.g., nitrogen) to the interior of reactor 200. In certain embodiments, polymerization reactor 200 may be equipped with at least two devices 100 for injecting one or more fluids into reactor 200. Furthermore, it is to be reiterated that device 100 is merely one embodiment of a tube that may extend into a reactor; for example, Figure 2 and Figure 3 The devices 100a-g shown in FIG. 1 may be replaced by a single tube, or other arrangements of inner and outer tubes extending into the interior of the reactor 200 substantially perpendicular to the sidewall 205 of the reactor 200 (substantially parallel to the distribution plate 210).

[0040] When more than one device 100 is used, the devices 100 may be equally spaced along the wall of the reactor 200 at the height at which the devices 100 are disposed along the reactor wall (i.e., when the reactor wall 205 is viewed as a circle in a top-down cross-section of the reactor, the devices 100 may be equally spaced along the circumference of the circle). For example, Figure 3 As shown, the device 100 can be oriented substantially horizontally within the reactor, and thus the first tube and the second tube of the device 100 are also oriented substantially horizontally. Alternatively, the devices 200 need not be equally spaced. For example, Figure 3 As shown, two or more devices 100 can be located on one side of the reactor or on the same half of the reactor wall at a cross section at the height at which the devices are arranged. Two or more devices 100 can be vertically spaced apart from each other, which means that along the reactor wall 205, one or more devices 100 can be located at a first height, and one or more other devices can be located at a second height that is higher or lower than the first height.

[0041] When used with a dry catalyst system, for example, a carrier fluid such as a carrier gas (e.g., nitrogen) may be used to deliver or carry the dry catalyst from a catalyst feeder through an injection tube 120 into the reactor 200 while the monomer or other hydrocarbon gas flows through the surrounding support tube 110. Preferably, in accordance with the foregoing description, the injection tube 120 may extend beyond the end of the surrounding support tube 110 (e.g., about 1 / 16" to 3", e.g., about 3 / 16") to ensure that the catalyst flowing through the injection tube 120 is swept away from the device 100 by the gas flowing through the surrounding support tube 120. Advantageously, this may also provide better detection of skinning via any impact on the inner tube extending further into the interior of the reactor 200. The flow rate and / or pressure drop of the carrier fluid (e.g., nitrogen) in the inner tube 120 or other fluid (e.g., hydrocarbon such as monomer and / or ICA and / or purge gas) flowing through the outer tube 110 may be measured and monitored, for example, using corresponding instruments 130, 135 to detect skinning formation within the reactor in real time.

[0042] When used together with a slurry catalyst system, one or more first groups of devices 100 can be used to detect crusting in the reactor, and one or more second groups of devices 100 can be used to inject the slurry catalyst system into the reactor. The first and second groups of devices 100 can be the same or different. For example, the first group can simply include a support tube 110 without including an internal smaller tube 120 to allow a single type of fluid to flow through the device 100. The second group can include both the support tube 110 and the internal injection tube 120. The second group can optionally include instruments 130, 135 to also detect and / or measure the fluctuation of flow rate and / or pressure drop. However, similarly, the first group (including a single tube) can also be equipped with an instrument or other device to measure the fluctuation of flow rate and / or pressure drop.

[0043] Typical slurry catalyst systems include solvents or suspensions used as carrier fluids; for example, mineral oil, hexane and / or other hydrocarbons, such as one or more ICAs (e.g., isopropane or n-propane, butane, pentane, etc.), which advantageously can serve as a suspension fluid for the catalyst and then as a coolant in the reactor. Therefore, the composition flowing through the tube in such slurry catalyst systems may include a carrier fluid, at least one catalyst compound, a carrier and an optional activator. The catalyst system may further include one or more optional light alkylates, such as triisobutylaluminum, aluminoxane, modified methylaluminoxane and / or trimethylaluminum. In the case of using an inner tube and an outer tube (e.g., each device 100), this combination is usually injected into the reactor 200 through the inner tube 120 of the device 100, and the purge fluid is injected into the reactor 200 through the surrounding support tube 110. A purge fluid (typically fresh monomer, ethylene, hexane, isopentane, recycle gas, etc.) may flow through support tube 110 to aid in the dispersion of the slurry catalyst composition injected through inner tube 120, thereby allowing the production of resin particles of good morphology with reduced agglomeration and an APS (average particle size) in the range of about 0.005 to 0.10 inches (0.01 cm to 0.3 cm). The purge fluid helps minimize fouling at the ends of catalyst injection tube 120 and support tube 110.

[0044] The purge fluid flowing through the support tube 110 (or other tubes according to the description herein) may be or may include any one or more of the following: hydrogen; olefins or diolefins, including but not limited to C2 to C 40 α-olefins and C2 to C 40 dienes, ethylene, propylene, butene, hexene, octene, norbornene, pentene, hexadiene, pentadiene, isobutylene, octadiene, cyclopentadiene, comonomers for polymerization, hydrogen; alkanes, these C1 to C 40 Alkanes, including but not limited to isopentane, hexane, ethane, propane, butane, etc.; mineral oil, recycle gas with or without condensate; or any combination thereof. Preferably, the support tube stream is fresh ethylene or propylene, which may be heated. In addition, ICAs, such as alkanes, such as isopentane or hexane, may be included in the fluid at a level of about 0.001 wt % to about 50 wt % of the fluid. The alkanes may be dispersed in the fluid and may be present as dispersed droplets or may evaporate at the outlet of the support tube. The presence of the liquid may reduce fouling at the outlet.

[0045] The flow rate of the fluid passing through the support tube 110 may be in the range of about 5 to 10,000 pph and depends to some extent on the reactor size and / or the diameter of the support tube 110. The linear velocity of the fluid in the support tube 110 may be in the range of about 10 to 500 ft / sec (11 km / hr to 549 km / hr), preferably about 20 to 300 ft / sec (22 km / hr to 329 km / hr), and more preferably about 30 to 200 ft / sec (33 km / hr to 219 km / hr).

[0046] In certain embodiments, the outlet of the support tube 110 may be tapered to form a gas jet or dispersion to aid in the distribution of the catalyst composition. In one embodiment, the inner diameter of the support tube 110 tapers from about 3% to 80% at the end, preferably tapers from about 5% to 50% to create a nozzle to accelerate and / or disperse the fluid flow. The insertion of the injection tube 120 is not affected by the inner taper of the support tube 110.

[0047] As described above, the device 100 can be used alone or in combination with one or more slurry catalyst injection nozzles and / or dry catalyst injection nozzles to detect the crusting in the reactor. Due to the small clusters or crusting of the polymer contacting the tip of the device 100, the instruments 130, 135 can detect the intermittent changes (also referred to as ΔP or DP for short) of the flow rate and / or pressure drop through the outer tube 110 or the inner tube 120 in real time. The short pulses of flow fluctuations and / or pressure changes through the outer tube 110 or the inner tube 120 indicate that some kind of blockage occurs at the end of the device 100, indicating that some kind of undesirable solid formation or crusting occurs in the reactor 200. Then the operation can use this information to take steps to mitigate the degree of undesirable solid formation and prevent the reactor from shutting down. In addition, by making the monomer gas instead of nitrogen flow through the device 100, the exhaust problem caused by the accumulation of inert gas can be avoided or at least significantly reduced. The device 100 can be used in a new facility, or an existing reactor can be refurbished to include the device 100. Similarly, an existing catalyst injection nozzle having separate flow channels may be modified to include the instruments 130, 135 and operated with monomer flow to detect intermittent changes in flow rate and / or pressure drop in real time.

[0048] All patents and patent applications, test procedures (eg, ASTM methods, UL methods, etc.), and other documents cited herein are fully incorporated by reference to the extent this disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

[0049] Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It is understood that ranges including combinations of any two values, such as any lower limit value combined with any upper limit value, any combination of any two lower limits, and / or any combination of any two upper limits are contemplated unless otherwise indicated. Certain lower limits, upper limits, and ranges appear in one or more claims below. All numerical values ​​are "about" or "approximately" indicated values, which means that these values ​​take into account experimental errors, machine tolerances, and other deviations expected by a person of ordinary skill in the art.

[0050] The foregoing also summarizes the features of several embodiments so that those skilled in the art can better understand the present disclosure. Those skilled in the art will appreciate that they can easily use the present disclosure as a basis for designing or modifying other methods or devices for performing the same purpose of the embodiments disclosed herein and / or realizing the same advantages of the embodiments disclosed herein. Those skilled in the art will also appreciate that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure, and that the scope is determined by the appended claims.

[0051] Various terms have been defined above. If a term used in a claim is not defined above, it should be given the broadest definition persons in the relevant art have given that term as reflected in at least one printed publication or issued patent. In addition, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent this disclosure is not inconsistent with the present invention and for all jurisdictions in which such incorporation is permitted. While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope of the invention is determined by the claims that follow.

Claims

1. A method for detecting initial skinning in a polyolefin gas phase reactor, comprising: flowing one or more fluids through a first tube extending through a reactor wall at a first height above a distributor plate within the reactor in a substantially horizontal orientation, wherein the first tube has an inner diameter less than or equal to 0.5 inches; measuring a pressure difference, a flow rate, or both of a fluid flowing through the first tube; detecting a decrease in a measured differential pressure, flow rate, or both of the fluid; and Based at least in part on the detected decrease in the measured pressure differential, flow rate, or both, one or more remedial actions are taken to control or reverse skinning in the reactor.

2. The method of claim 1, wherein the first tube is disposed within a second tube, the inner diameter of the second tube being greater than the outer diameter of the first tube, and further wherein the first tube and the second tube are concentric such that an annular space is defined between the first tube and the second tube.

3. The method of claim 2, wherein the second tube is rigid.

4. The process of claim 2 or claim 3, wherein the first tube extends into the reactor at least 0.1875 inches beyond the second tube.

5. The method of claim 2 or any one of claims 3-4, wherein a pressure drop, flow rate, or both along the second tube is measured, and further wherein a decrease in the pressure drop, flow rate, or both along the second tube is detected, and one or more remedial actions are taken to control or reverse skinning in the reactor based at least in part on the detected decrease in the pressure drop, flow rate, or both along the second tube.

6. The method of claim 1 or any one of claims 2-5, wherein the first tube is flexible.

7. The process of claim 1 or any one of claims 2 to 6, wherein the first tube extends into the reactor a distance in the range of 1 / 10 to 1 / 3 of the diameter of the reactor.

8. The process of claim 1 or any one of claims 2-7, wherein the first height is between 0.2 feet and 20 feet above a distributor plate within the reactor.

9. The method of claim 1 or any one of claims 2-8, wherein the detected decrease in the measured pressure differential, flow rate, or both exceeds a predetermined threshold.

10. The method of claim 9, wherein the predetermined threshold is a decrease of at least 30% over a period of 1 minute or less compared to the measured pressure differential, flow rate, or both immediately preceding the measured decrease.

11. The process of claim 1 or any one of claims 2-10, wherein the one or more remedial measures include one or more of: reducing the feed rate of one or more monomers to the reactor; reducing the reactor temperature; reducing the feed rate of one or more condensing agents to the reactor; venting a portion of a reactor overhead; reducing the feed rate of catalyst to the reactor; changing the target melt index and / or density of the polymer being produced in the reactor; and changing the height of the fluidized bed within the reactor.

12. The method of claim 1 or any one of claims 2-11, wherein the inner diameter of the first tube is 0.25 inches or less.

13. The method of any of the preceding claims, wherein the one or more fluids flowing through the first tube comprises one or more of the following: a carrier fluid containing solid catalyst particles, a monomer gas, an induced condensing agent, and a purge gas.

14. A method for the polymerization of olefins in a gas phase reactor, comprising: injecting a catalyst mixture into the gas phase reactor via one or more catalyst injectors, each catalyst injector extending substantially horizontally through the reactor wall at a first height within the reactor above a distributor plate within the reactor, wherein each catalyst injector comprises a first tube disposed within a second tube, the second tube having an inner diameter greater than an outer diameter of the first tube, thereby forming an annular space therebetween, wherein the catalyst mixture flows through the first tube, and an additional fluid flows through the second tube, and further wherein the catalyst mixture comprises a plurality of solid catalyst particles and a carrier fluid; introducing one or more monomer gases into the reactor; polymerizing the one or more monomer gases in the presence of the catalyst particles within the reactor to form solid polymer particles; measuring the pressure difference and / or the flow rate along the first tube and / or along the second tube; and Based at least in part on the detected decrease in the measured pressure differential and / or flow rate, one or more remedial actions are taken to control or reverse skinning in the reactor.

15. The process of claim 14, wherein the catalyst mixture comprises the plurality of solid catalyst particles entrained in an inert carrier gas or slurried in a solvent.

16. The method of claim 14 or claim 15, wherein the one or more monomer gases are injected into the reactor via one or more monomer injectors, the one or more monomer injectors substantially horizontally penetrating the reactor wall at a second height above a distribution plate within the reactor, and further wherein each monomer injector comprises a first monomer injector tube disposed within a second monomer injector tube, the second monomer injector tube having an inner diameter greater than an outer diameter of the first monomer injector tube, thereby forming an annular space therebetween, wherein the one or more monomer gases flow through both the first and second monomer injector tubes.

17. The method of claim 16, wherein the second height of the one or more monomer injectors is below the first height of the one or more catalyst injectors.

18. The method of claim 16 or claim 17, wherein the at least one monomer injector comprises four monomer injectors equally spaced along the reactor wall at the second height of the reactor.

19. The process of claim 14 or any one of claims 15-18, wherein the one or more catalyst injectors comprise four catalyst injectors equally spaced along the reactor wall at the first height of the reactor.

20. The method of claim 14 or any one of claims 15-19, wherein the remedial measures include one or more of the following: reducing one or more monomer feeds through the first tube, the second tube, or both tubes; discharging a reactor overhead stream to a flare; and Increase the polymer bed level.

21. A method for refurbishing a gas phase polymerization reactor using slurry injection, the method comprising: adding one or more devices for injecting one or more fluids into the reactor, each device comprising at least one flow path therethrough and one or more instruments for measuring pressure variation pulses along said flow path, wherein said one or more devices are located below a catalyst injection nozzle for slurry injection and above a distribution plate within said reactor; flowing a fluid through each of the one or more added devices; Intermittent pressure drops across each device were monitored to detect skin formation within the reactor.

22. The method of claim 21, wherein the flow path through the device has a first end that is flush with the inner surface of the reactor wall.

23. The process of claim 21 wherein the flow path through the apparatus has a first end extending beyond the interior surface of the reactor wall into the fluidized bed region within the reactor.

24. The method of claim 20 or any one of claims 22-23, further comprising any one or more of the following remedial adjustments if the measured pressure differential exceeds a predetermined amount: reducing a feed rate of one or more monomers through the first tube, the second tube, or both tubes; discharging a reactor overhead stream to a flare; and Increase polymer bed level.

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