RU2781188C1 - System and method for rapid heating of the drain tank - Google Patents

Abstract

FIELD: polymer production.

SUBSTANCE: group of inventions relates to the field of polymer production, in particular to a drain tank for moving the contents of the reactor into it. The method for operation of the drain tank involves moving all or part of the contents of the polymerization reactor into the drain tank. Moreover, the contents of the reactor include a solid polymer, as well as liquid and gaseous non-product components. Then, at least parts of liquid and gaseous non-product components are extracted from the drain tank by reducing the pressure in the drain tank, the solid polymer is subjected to the first purification stage, including heating of the solid polymer by introducing the first heated treatment gas into the drain tank, and the solid polymer is subjected to the second purification stage, including purging of the solid polymer by introducing the second heated treatment gas into the drain tank.

EFFECT: improvement of the process of unloading the contents of the polymerization reactor.

18 cl, 6 dwg

Description

FIELD OF TECHNOLOGY

[0002] The disclosed apparatus, systems, and methods relate to transferring (eg, "dumping") the contents or stock of one or more polymerization reactors into a drain vessel (eg, "dumping" tank). More specifically, the disclosed devices, systems, and methods relate to improved overflow tanks and methods for recovering non-product components from a polymerization reactor stock containing polymer flakes transferred to the overflow tank during polymerization reactor unloading. Even more specifically, the disclosed devices, systems, and methods relate to improved methods for recovering non-product components from a stock of a polymerization reactor transferred to an overflow tank during a discharge of a polymerization reactor, by cleaning polymer flakes by contacting a stock of a polymerization reactor transferred to an overflow tank with a first heated a treatment gas containing mainly hydrocarbons, followed by purging the overflow tank with a second heated treatment gas containing mainly nitrogen.

BACKGROUND OF THE INVENTION

[0003] Under certain abnormal operating situations in a polymerization plant, such as, but not limited to, power system losses (e.g., power), steam losses, circulation pump/circulation pump seal losses, reactor outlet losses, or any other significant In cases where continued circulation or the presence of polymer in the polymerization reactor is undesirable, the polymerization reactor must be diverted, drained or emptied quickly (eg, "drain" the contents or "stock" of the polymerization reactor). For this purpose, polymerization plants are usually equipped with drain tanks.

[0004] In large installations, the time period required to recover residual hydrocarbons from the polymer flakes transferred to the overflow tank (also referred to as the polymer bed) can be very long, sometimes more than 7 days. The recovery of residual hydrocarbons from the flakes can sometimes become a critical path under shutdown conditions, and it is desirable that the recovery process be accelerated. The hydrocarbon recovery process can take a long time because the residual liquids must be evaporated and the residual hydrocarbons sorbed into the polymer layer must be purified. Both of these processes are highly dependent on temperature and heat input, and conventional plants have a limited ability to introduce significant amounts of heat into the stagnant non-flowing layer of polymer and liquids in the overflow tank. Traditionally, the overflow tank is equipped with a steam jacket on a conical bottom. However, the polymer is a fairly good insulator and there is also a significant risk of melting in the cone of stagnant, entrained lower density polymers, making it difficult to discharge the polymer from the overflow tank after being dehydrocarbonated by heating using such a steam jacket.

[0005] Accordingly, there is a need for systems and methods to improve the process of unloading from the polymerization reactor.

SUMMARY OF THE INVENTION

[0006] Disclosed herein is a method of operating an overflow tank of a polymer production process, the method comprising: transferring all or part of the contents of a polymerization reactor to an overflow tank, wherein the reactor contents include solid polymer as well as liquid and gaseous non-product components; and removing at least a portion of the liquid and gaseous non-product components from the overflow reservoir by: depressurizing the overflow reservoir, whereby a flash gas containing a first portion of at least a portion of the liquid and gaseous non-product components is removed from the overflow reservoir; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first a gas containing a second portion of at least a portion of the liquid and gaseous non-product components from the overflow tank during the first purification step; and subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas containing a third of at least a portion of liquid and gaseous non-product components from drain tank during the second stage of cleaning.

[0007] Also disclosed herein is a system comprising: an overflow tank into which all or part of the contents of the polymerization reactor can be transferred during discharge of the polymerization reactor in a polymer production process, the overflow tank comprising: a gas distribution system configured to distribute gas processing introduced into it through the inlet line of the treatment gas, essentially uniformly across the cross section of the overflow tank, while the gas distribution system is located in the lower part of the overflow tank; a heater configured to raise the temperature of the treatment gas to the temperature of the treatment gas; a helmet pipeline connecting the drain tank with a torch in a fluid medium; and a ventilation filter on the helmet conduit, wherein the ventilation filter is configured to trap entrained polymer particles in the gas passing through the helmet conduit.

[0008] Also disclosed herein is a process for producing polyolefins, comprising: (i) during normal operation: polymerizing a polymerization feedstock containing a monomer, a diluent, and optionally a comonomer, in the presence of a polymerization catalyst to obtain a polymerization effluent containing solid polymer, as well as liquid and gaseous non-product components; passing the polymerization reactor effluent through one or more flash line heaters configured to indirectly heat the polymerization reactor effluent; separating one or more non-product components from the polymerization reactor effluent using a separation device; and recycling at least one of the one or more separated non-product components to the polymerization reactor through a recycle line, and (ii) during the discharge of the polymerization reactor: transferring all or part of the contents of the polymerization reactor to an overflow tank, wherein the contents of the reactor include a solid polymer, and also liquid and gaseous non-food components; and removing at least a portion of the non-product components from the overflow reservoir by: depressurizing the overflow reservoir, whereby a flash gas containing a first portion of at least a portion of the non-product components is removed from the overflow reservoir; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first gas containing the second part of at least part of the non-product components from the drain tank during the first stage of purification; and subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas containing a third of at least a portion of non-product components from the overflow tank into during the second purification step.

BRIEF DESCRIPTION OF GRAPHICS

[0009] In the detailed description, reference will be made to the drawings, briefly described below, where like reference numerals refer to like parts, unless otherwise indicated.

[0010] In FIG. 1 schematically illustrates an overflow reservoir system 10 in accordance with embodiments of this invention;

[0011] In FIG. 2 schematically illustrates a polymerization system I in which the overflow tank of FIG. 1 in accordance with embodiments of this invention;

[0012] In FIG. 3 schematically illustrates an integrated polymerization system II comprising an overflow reservoir system 10 in accordance with embodiments of this invention;

[0013] In FIG. 4 schematically illustrates an overflow reservoir 12 in accordance with embodiments of this invention;

[0014] In FIG. 5 is a plot of the maximum heating rate per unit cross-sectional area as a function of overflow tank backpressure and reduced rate as described in Example 1; and

[0015] In FIG. 6 is a plot of isobutane flow as a function of overflow tank backpressure and reference velocity as described in Example 1.

DETAILED DESCRIPTION

[0016] With reference to FIG. 1, which illustrates a simplified diagram of a downcomer system 10 in accordance with embodiments of this invention, this document discloses a method of operating a downcomer of a polymer manufacturing process (e.g., a polyolefin manufacturing process, e.g., a polyethylene block), which method includes: stock (also called polymer amount, or reactor content, or reaction mixture) of polymer (also called polymer flakes, polymer particles, solid product polyolefin, etc.) from the polymerization reactor to the overflow tank, wherein the stock of polymer flakes contains solid product polyolefin, as well as liquid and gaseous non-product components (also referred to in this document as "non-solid" components); and removing at least a portion of the non-product components from the overflow reservoir by: depressurizing the overflow reservoir (e.g., depressurizing) whereby a flash gas containing a first portion of at least a portion of the liquid and gaseous non-product components is removed from the overflow reservoir along helmet pipeline; subjecting the polymer fluff to a first purification step, which includes heating the polymer fluff by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the polymer fluff in the first purification step is reached, and withdrawing the first a gas (also referred to as the first off-gas) containing a second portion of at least a portion of the liquid and gaseous non-product components from the overflow tank during the first purification step; and subjecting the polymer fluff to a second purification step, comprising blowing the polymer fluff by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas (also referred to as a second exhaust gas) containing a third of at least part liquid and gaseous non-product components from the drain tank during the second stage of purification. The combination of the first part, the second part, and the third part (e.g., at least a portion of non-food ingredients) in embodiments of the invention may include substantially all (e.g., about 80, 85, 90, 95, 99, or 100% or more) liquid and gaseous non-food polymerization reactor stock components. The first and second purification stages may also be referred to as the first and second purge stages, respectively, and the first and second treatment gases may also be referred to as the first and second purge gases, respectively.

[0017] With reference to the embodiment of the invention of FIG. 1, during the polymerization reactor drain process, the polymerization reactor stock is removed from the polymerization reactor and introduced into the overflow tank system 10 via the overflow tank supply line 11 . With reference to FIG. 2, which schematically illustrates a polymerization system I in which an overflow tank according to this invention can be used (for example, overflow tank system 10 of FIG. 1), in accordance with embodiments of this invention, the overflow tank supply line 11 (in FIG. 1) may be in fluid communication with the polymerization reactor 21, for example, via an overflow tank feed line 11 connected to a reactor effluent line 26 used to convey the polymerization reactor effluent to a downstream in-process separation system 40 polymerization and/or overflow tank supply line 11 connected to one or more special discharge lines 27 used to move stock of the polymerization reactor to the overflow tank during unloading of the polymerization reactor. For example, without limitation, during the unloading of the polymerization reactor, stock of the polymerization reactor may be introduced into the overflow tank system 10 through the overflow tank supply line 11 connected to the reactor effluent line 26 before or after the first inline flash heater (also referred to herein as "flash line heater"), a second inline flash heater (e.g., a second flash line heater), or a third inline flash heater 30C (e.g., a third flash line heater), such as along section 31A, 31B, or 31C, respectively. , line 26 of the polymerization reactor effluent. Alternatively, stock of the polymerization reactor may be introduced into the overflow tank system 10 via the overflow tank feed line 11 connected to the solids outlet conduit 41, as described herein below with reference to FIG. 3 and/or via a drain tank supply line 11 connected to one or more dedicated discharge lines 27. Embodiments of the invention use a plurality of overflow tank feed lines 11 connected to the polymerization reactor 21 as described above to move stock of the polymerization reactor 21 into the overflow tank system 10 during unloading of the polymerization reactor. After the first and second cleaning steps, as described herein, the overflow reservoir stock may be removed from the overflow reservoir 12 via a discharge line 8, through one or more valves V _a /V _b and a container (e.g. hopper) 9.

[0018] With reference to FIG. 1, one or more helmet lines may be used to withdraw the flash gas, the first gas (for example, the first off-gas) and the second gas (for example, the second off-gas) from the discharge tank 12 during the depressurization process, the first stage of cleaning and the second stage cleaning, respectively. The first helmet conduit 20A can fluidly connect the downcomer 12 to the flare, whereby the gas exiting the downcomer 12 through the first helmet conduit 20A can be directed to the flare. A vent filter 30 may be located on the first vent 20A (and/or the second vent 20B and/or the third vent 20C) so that entrained particulate matter can be removed from the gas passing through it before flaring. The second helmet conduit 20B and/or the third helmet conduit 20C may connect the fluid overflow reservoir 12 to the separation device 40 described below with reference to FIG. 2 and 3. For example, the second helmet conduit 20B may connect the overflow reservoir 12 via fluid to the flash chamber 32 of the separation device 40, which is also described below with reference to FIG. 3. Alternatively or additionally, a third helmet conduit 20C may connect a fluid overflow reservoir 12 to a nitrogen separator (eg, INRU), as also described below with reference to FIG. 3.

[0019] The stock of the polymerization reactor may be fed into the pressure overflow tank system 10 . In embodiments of the invention, after the stock of the polymerization reactor is transferred to the overflow tank system 10, the overflow tank system 10 is isolated from the polymerization reactor (for example, using one or more valves in the overflow tank supply line 11) and the pressure in the overflow tank 12 is reduced, as a result whereby a flash gas containing a first portion of at least a portion of the non-product components is generated and is withdrawn from the overflow tank 12 via the head conduit 20A, 20B or 20C. In embodiments of the invention, during the discharge of the polymerization reactor 21, the flash through the separating device removes the flash gas before introducing the first heated treatment gas or the second heated treatment gas into the overflow tank 12.

[0020] As noted above, removing at least a portion of the non-product components from the overflow reservoir may include depressurizing (i.e. depressurizing) the overflow reservoir, thereby generating a flash gas containing a first portion of at least a portion of the liquid and gaseous non-product components, and are removed from the drain tank through the helmet pipeline. In embodiments of the invention, flashing is accomplished by opening a valve V _C between the sump system 10 and the flashing chamber 32 (described below with reference to FIG. 3) of the separation device 40, with the flash gas passing through a helmet piping (e.g., helmpipe). 20B) through which a flash gas containing a first portion of at least a portion of non-product components is introduced into the flash chamber 32 of the separation apparatus 40 described further below. In such embodiments, a separation device may be used to separate one or more non-product components, e.g., diluent (e.g., isobutane (iC ₄ )), hydrocarbon treatment gas (e.g., iC ₄ , fuel gas), monomer (e.g., ethylene), comonomer (eg hexane) or combinations thereof from a flash gas. In embodiments of the invention, the flashing comprises venting gas from the overflow tank 12 to the nitrogen separator 45 (e.g., INRU) of the separation device 40 (described below with reference to FIG. 3) through the top conduit (e.g., third conduit 20C), through which the flash gas containing the first part of at least part of the non-product components is introduced into the nitrogen separator 45 of the separation device 40 described below.

[0021] In accordance with this disclosure, removing at least a portion of the non-product components from the downcomer includes subjecting the polymer flakes from the transferred stock of the polymerization reactor in the overflow tank system 10 to a first purification stage (also referred to herein as the first purge stage) involving heating the polymer flake by introducing a first heated treatment gas containing primarily one or more hydrocarbons (also referred to herein as a heated hydrocarbon treatment gas) into the overflow tank 12 until the temperature of the first stage of purification of the polymer flakes is reached, and removing a first gas (eg, a first exhaust gas) containing a second portion of at least a portion of the liquid and gaseous non-product components from the overflow tank 12 during the first purification step.

[0022] In accordance with this disclosure, the heated hydrocarbon treatment gas introduced into the overflow tank 12 during the first purification step contains, consists essentially of, or consists of one or more hydrocarbons having from one to five carbon atoms (hydrocarbons C1-C5 ). In embodiments of the invention, the heated hydrocarbon treatment gas comprises, essentially consists of, or consists of isobutane, isopentane, fuel gas, propane, propylene, or a combination thereof. Used in this document, the term "fuel gas" includes natural gas, for example, fed through the pipeline to the plant. For example, the fuel gas may contain or consist of 90% wt. or more of methane, with the remainder consisting primarily of ethane, carbon dioxide, nitrogen, and/or other minor amounts of lighter hydrocarbon gases that may accompany natural gas in pipelines. In one embodiment of the invention, the heated hydrocarbon treatment gas contains, essentially consists of, or consists of isobutene. In embodiments, the heated hydrocarbon treatment stream contains less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5 or 0.1% wt. gas components other than C1-C5 hydrocarbons.

[0023] In accordance with this disclosure, removing at least a portion of the non-product components from the overflow tank further comprises, after the first cleaning stage, subjecting the polymer flakes in the overflow tank system 10 to a second cleaning stage (also referred to herein as a second purge stage) comprising purging the polymer flake by introducing into the overflow tank 12 a second heated treatment gas (also referred to as heated nitrogen treatment gas) containing substantially consisting of or consisting of nitrogen, and recovering a second gas (e.g., a second exhaust gas) containing a third of the at least part of the liquid and gaseous non-product components, from the drain tank 12 during the second stage of purification. In embodiments of the invention, the second heated treatment gas contains less than 50, 45, 40, 35, 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1% wt. gas components other than nitrogen. Thus, after the heating provided by the first purification step, the nitrogen purge can be carried out during the second purification step, in embodiments of the invention, during the period of time for the extraction of residual hydrocarbons from the polymer and the surrounding vapor space in the overflow tank 12. The first and/or the second stage cleaning can continue in embodiments of the invention until the lower explosive limit (LEL) is reached, less than or equal to 10, 5, 4, 3, 2, 1, or essentially 0% vol. The LEL used herein is defined as the concentration of combustible hydrocarbon gases in the vapor space using various mechanisms depending on the meter used for the measurement (e.g. infrared absorption, catalytic bead combustion, etc.) in %LEL.

[0024] The heated treatment gas (eg, the heated hydrocarbon treatment gas of the first purification stage and the heated nitrogen treatment gas of the second purification stage) is introduced into the overflow tank 12 at a temperature below the melting temperature of the polymer flakes. The hydrocarbon treatment gas may be introduced through the hydrocarbon treatment gas line 15B and the treatment gas line 15 into the gas heater 6 (eg, a steam heater) for heating to produce a heated hydrocarbon treatment gas. Nitrogen may be introduced via nitrogen gas line 15A and process gas line 15 to heater 6 or other preheater to produce a second heated process gas. The heated treatment gas (eg, heated hydrocarbon treatment gas in the first purification stage, heated nitrogen treatment gas in the second purification stage) may be introduced into the overflow tank 12 via the heated treatment gas line 15'. The heater 6 used to heat the first treatment gas (e.g., hydrocarbons as described above) and produce the first heated treatment gas and/or heat the nitrogen and produce the second heated treatment gas may be any suitable heater known to those skilled in the art for heating the treatment gas to a desired temperature to obtain a heated treatment gas. In embodiments of the invention, heater 6 is a steam heater. In embodiments of the invention, heater 6 is a shell and tube heater. In embodiments of the invention, the heater 6 used to heat the first treatment gas comprises one or more flash line heaters (e.g., 30A, 30B, 30C of FIGS. 2 and 3) of the polymerization system (e.g., polymerization system I of FIG. 2 or of the integrated polymerization system II of Fig. 3) as described below with reference to the embodiment of the invention illustrated in Figs. 2 and 3. In embodiments of the invention, a different or the same heater 6 is used to heat the nitrogen for introduction into the overflow tank during the second purification stage. For example, if one or more flash line heaters are used to heat the first treatment gas, then for heating nitrogen to produce a second treatment gas, another heater may be used.

[0025] In embodiments of the invention, a first heated treatment gas (eg, a heated hydrocarbon treatment gas) introduced into the overflow tank 12 during the first purification step and/or a second heated treatment gas (eg, heated nitrogen) introduced into the overflow tank 12 during the second purification step, has a temperature that is in the range of about 85 to about 95, about 80 to about 90, or about 90 to about 95% of the melting point of the polyolefin flakes (e.g., polyethylene homopolymer or polyethylene copolymer, e.g., copolymer of ethylene and 1-hexene). In embodiments of the invention, a first heated treatment gas (e.g., a heated hydrocarbon treatment gas) introduced into downcomer 12 during the first purification step and/or a second heated treatment gas (e.g., heated nitrogen) introduced into downcomer 12 during the second cleaning stage, has a temperature that is in the range from about ambient temperature to about 200°F (about ambient temperature to about 93.3°C), from about 68°F to about 200°F (about 20° C to about 93.3°C), from about 68°F to about 190°F (from about 20°C to about 87.8°C), from about 70-90°F to about 190-200°F ( from about 21.1-32.2°C to about 87.8-93.3°C), from about 70-90°F to about 160-180°F (from about 21.1-32.2°C up to about 71.1-82.2°C). To prevent condensation of the hydrocarbon treatment gas inside the overflow tank 12, in embodiments of the invention, the hydrocarbon treatment gas may be superheated by the heater 6 to a temperature above its dew point before being supplied to the overflow tank 12.

[0026] In embodiments of the invention, backpressure is maintained in the overflow reservoir during the first purification step. For example, in embodiments of the invention, the backpressure in the overflow reservoir is maintained during at least the first stage of cleaning greater than or equal to about 5, 70, 100, or 130 psig. (0.0345, 0.4826, 0.6895, or 0.8963 MPa) or in the range of about 5 to about 130 psig, about 5 to about 70 psig, from about 5 psig up to about 30 psig (0.2068 MPa) or from about 70 to about 130 psig. Maintaining backpressure in the overflow reservoir may allow the use of a lower superficial velocity of the heated hydrocarbon treatment gas while using a higher mass flow rate of the heated hydrocarbon treatment gas (eg, isobutane).

[0027] The introduction of the treatment gas (e.g., heated hydrocarbon treatment gas during the first purification stage and heated nitrogen treatment gas during the second purification stage) may be at a rate greater than or less than the minimum fluidization rate for the polymer bed in the overflow tank 12 In embodiments of the invention, the heated hydrocarbon treatment gas introduced into the overflow tank 12 during the first purification stage and/or the heated nitrogen treatment gas introduced into the overflow vessel 12 during the second purification stage are introduced at a reduced rate that is below the minimum fluidization rate. polymer flakes in downcomer 12. Maintaining the reduced rate below the minimum fluidization rate can advantageously reduce the amount of entrained fines from above (e.g., exiting downcomer 12 at flows 20A, 20B, or 20C) during the first cleaning step and/or the second cleaning step.

[0028] As will be appreciated by one of ordinary skill in the art and with the aid of this disclosure, in embodiments of the invention where the rate is limited to a particular maximum rate due to fluidization criteria, there may be a need to choose between the backpressure maintained in the overflow reservoir 12, the resulting density hydrocarbon treatment gas (e.g., isobutane), the saturation/dew point temperature of the hydrocarbon treatment gas (e.g., isobutane), the maximum temperature that can be used without melting the polymer fluff (e.g., 190°F), and the maximum steam heating rate of the hydrocarbon treatment gas.

[0029] In embodiments of the invention, the flow of heated treatment gas (e.g., heated hydrocarbon treatment gas during the first purification stage and heated nitrogen treatment gas during the second purification stage) is increased such that the reduced rate is greater than or equal to the minimum fluidization rate used, and the polyolefin flakes are fluidised. In such embodiments, appropriate fluidization criteria may be taken into account, for example, inclusion of a grid plate, separation of fine particles, etc., which will be understood by those skilled in the art and with the help of this disclosure.

[0030] In embodiments of the invention, the temperature of the first cleaning step, defined as the internal temperature to which the polymer flakes are brought during the first cleaning step, is in the range of from about 85 to about 95, from about 80 to about 90, or from about 90 to about 95% melting temperature of polymer flakes. In embodiments, the temperature of the first purification step is a temperature in the range of about 120 to about 190°F (about 49 to about 87°C), about 120 to about 130°F (about 49 to about 54°C), about 150 to about 190°F (about 65 to about 87°C), about 160 to about 190°F (about 71 to about 87°C), about 150 to about 180°F (about 65 up to about 82°C), or greater than or equal to about 150, 160, 170, 180, or 190°F (about 65, 71, 76, 82, or 87°C). In embodiments of the invention, the first cleaning step is performed until bed temperature measurements are within 10 or 15° F. of the inlet temperature to avoid excessive waiting time for the last heat to occur.

[0031] In embodiments of the invention during the first stage of cleaning, the heating rate per cross-sectional area of the overflow tank 12, greater than or equal to about 5000, 6000 or 7000 BTU/hr·ft ² , (15.76, 18.91 or 22.07 kW/m ² ) is provided by the introduction of the first heated treatment gas (eg hydrocarbon heated treatment gas). In embodiments of the invention, the method of operating the downcomer system 10 according to this disclosure further includes selecting the flow rate of the heated hydrocarbon treatment gas, the temperature of the heated hydrocarbon treatment gas introduced into the downcomer 12 during the first stage of cleaning, the back pressure in the downcomer 12 during the first stage cleaning or a combination thereof to minimize the time of the first stage of cleaning, while the time of the first stage of cleaning is the duration of the first stage of cleaning. In embodiments of the invention, the temperature of the first purification stage is reached in a first purification stage time less than or equal to approximately 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9 , 8, 7, 6, 5, 4, 3, 2 hours or 1 hour. In embodiments of the invention, by selecting first stage cleaning conditions as described herein, heating the layer of polymer flakes in the downcomer 12 to the temperature of the first stage cleaning can be carried out during the first stage cleaning time from about 4 to about 8 hours, from about 12 until about 6 p.m. or from about 4 to about 8 p.m.

[0032] In embodiments of the invention, the method of operating the overflow reservoir, including the depressurization step and the first and second cleaning steps, can be performed in a total cleaning time less than or equal to about 24, 23, 22, 21, 20, 19, 18, 17 , 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2 hours or 1 hour.

[0033] In embodiments of the invention, the time required to extract at least a portion of the liquid and gaseous non-product components from the polymer flakes (for example, by extracting the flash gas, the first gas and the second gas from the discharge reservoir 12) is less than or equal to about 10, 20 , 30%, 40%, 50%, 60%, 70% or 80% of the time required to extract the same at least part of the non-product components from the same polymer flakes in the same way, with the difference that only a heated treatment gas is used, containing mainly , nitrogen, without a first scrubbing step, wherein a first treatment gas containing primarily one or more hydrocarbons (e.g., isobutane) is introduced into the overflow tank 12 (i.e., without a first scrubbing step and undergoing only a second nitrogen scrubbing step ).

[0034] In embodiments of the invention, a first heated treatment gas (e.g., a heated hydrocarbon treatment gas) introduced into the downcomer 12 during the first purification step, and/or a second heated treatment gas (e.g., a heated nitrogen treatment gas) introduced into the overflow reservoir 12 during the second cleaning step is introduced into the bottom (eg bottom 10%, 20%, 30%, 40% of the total height _Ht ) of overflow reservoir 12 as described below with reference to FIG. 4, which schematically illustrates an overflow reservoir 12 in accordance with embodiments of this invention.

[0035] In embodiments of the invention, the heated treatment gas (e.g., the heated hydrocarbon treatment gas in the first purification stage and/or the heated nitrogen treatment gas in the second purification stage) is introduced into the overflow tank 12 through the gas distribution system 7 configured to substantially evenly distribute of the heated treatment gas over the cross-sectional area of the downcomer 12, while allowing the polymer to flow down and then the treatment gas is introduced therein. The gas distribution system 7 may be, or may resemble, a gas distribution system in a purge column (e.g., purge column 42, described below), or alternatively, it may be, or may be similar to, a fluidized bed grid plate, or it may be any suitable mechanism for distributing the gas in the polymer bed while allowing the polymer to flow downward after cleaning/degassing. In embodiments of the invention, the gas distribution system comprises a fluidized bed grid plate, J-purge™, a gas distributor (eg, an annular gas distribution manifold), or a combination thereof.

[0036] In embodiments of the invention, the first gas withdrawn from the downcomer system 10 during the first cleaning step is removed from the downcomer 12 through a helmet conduit (e.g., first helmet conduit 20A) and sent to the flare after it has been filtered (e.g., in a vent filter 30). Alternatively, the first gas withdrawn from the downcomer system 10 during the first purification step is removed from the downcomer 12 through a helmet conduit (e.g., a second helmet conduit 20V or a third conduit 20C) fluidly connected to the separation device 40 , and one or more components (e.g., hydrocarbons, diluent, hydrocarbon processing gas) may be separated from it prior to recycling (e.g., recycling hydrocarbons and/or diluent to polymerization reactor 21; recycling hydrocarbon processing gas to downcomer system 10 and/or recirculation of the diluent to the overflow tank system 10 when the diluent is a hydrocarbon treatment gas such as isobutane) or before they are flared. In embodiments of the invention, the second gas removed from the downcomer system 10 during the second stage of cleaning is removed from the downcomer 12 through the helmet pipeline (for example, the first helmet pipeline 20A) and is sent to the flare after it is filtered (for example, in the vent filter 30) . Alternatively, the second gas withdrawn from the downcomer system 10 during the second purification step is removed from the downcomer 12 via a helmet conduit fluidly connected to the separation device 40 (e.g., a second conduit 20B or a third conduit 20C), and one or more components (eg, hydrocarbons, nitrogen) are separated from it prior to recycling (eg, hydrocarbon recycling to reactor 21, nitrogen recycling to overflow tank 12) or prior to flaring. For example, in embodiments of the invention, the polyolefin production process includes a nitrogen separator 45 (for example, an isobutane and nitrogen recovery unit (INRU), as described below with reference to Fig. 3, and at least part of the nitrogen introduced into weir tank system 10 as a second treatment gas in the second purification stage contains nitrogen recovered and recycled from nitrogen separator 45. In embodiments of the invention, a second gas containing nitrogen and purified residual hydrocarbons is introduced through a third helmet line 20C into separator 45 nitrogen, and the nitrogen in the nitrogen line 46, separated from it in the nitrogen separator 45, is returned to the overflow tank system 10 (for example, through line 15A connected to the nitrogen line 46) for use as a gas for the second treatment (for example, nitrogen treatment gas ) during the second purification step. bottom stream 48V, separated from the second gas in the nitrogen separator 45, can be subsequently returned to the polymerization reactor 21 immediately after their return to the process. In such embodiments, fresh nitrogen (for example, via line 15A connected to fresh nitrogen line 47) can be used as the second part of the second treatment gas after return nitrogen from the nitrogen separator 45 used as the first part of the second treatment gas.

[0037] As will be understood by those skilled in the art and with the aid of this disclosure, the nitrogen purge in the second purification stage and flaring requires the addition of fuel gas (e.g., adding fuel gas after the heated nitrogen treatment gas is withdrawn from purge tank 12) to provide a minimum calorific value for combustion efficiency as well as the formation of NOx emissions. In embodiments of the invention in accordance with this disclosure, the use of a first heated treatment gas containing mainly hydrocarbons during the first stage of purification, and not only a nitrogen purge to purge the downcomer 12, can reduce the amount of NOx emissions generated during the purge process. overflow tank 12. In embodiments of the invention, the first gas and/or the second gas is flared, and the method disclosed herein produces an amount of NOx emissions from combustion that is less than or equal to the amount of NOx emissions produced by the same method, with the difference that only a heated treatment gas containing primarily nitrogen is used, without a first treatment gas containing primarily one or more hydrocarbons (i.e. purging the downcomer using only nitrogen without a first treatment step using hydrocarbons such as isobutane ).

[0038] As illustrated in FIG. 4, in embodiments of the invention, the overflow tank 12 is a generally cylindrical container having a lid section 1, a conical bottom section 2 and a straight section 3. The straight section 3 of the tank 12 is located above the conical bottom section 2 and may have a height H ₃ in range from about 8-10 to about 80-100 feet or more (from about 2.4-3.0 to about 24-30 meters or more). The straight section 3 of the tank 12 may have an internal diameter D ₁ in the range of about 6 to about 25 feet (about 1.8 to about 7.6 m). In embodiments of the invention, the lid 1 of the tank 12 may have a height H ₁ approximately twice the diameter D ₁ . In embodiments of the invention, the lid 1 of the reservoir 12 is ellipsoidal and H ₁ is about 20%, 25%, 30%, 40% or 50% of D ₁ . The conical bottom section 2 may have a height H ₂ in the range of about 3 to about 35 feet (about 0.9 to about 10.6 m). In embodiments of the invention, the conical bottom section 2 forms an angle α less than or equal to 45, 60 or 70 degrees from the horizontal. The use of such an angle α can minimize the amount of polymer flakes below the gas distribution system 7. Section 4 can be located under the conical bottom section 2. Section 4 can have an insert to change the flow of gas (for example, processing gas) introduced into it, for example, without being limited to this , J-purge™ overlay by Jenike and Johanson, Chinese hat or Binsert insert. Section 4 may have straight sides with a height H ₄ ranging from about 2 to about 12 feet (about 0.6 to about 3.6 m). Section 4 of tank 12 may have an internal diameter D ₂ in the range of about 2 to about 12 feet (about 0.6 to about 3.6 m). The shank 5 may be located under the section 2 and/or 4 of the conical bottom, if any. Shank 5 may be conical. In embodiments of the invention, the liner 5 may have a height H ₅ in the range of about 1 to about 17 feet (about 0.3 to about 5.1 m), about 1 to about 20 feet (about 0.3 to about 6 .0 m) or about 2 to about 20 feet (about 0.6 to about 6.0 m). The shank 5 may have an outlet diameter D ₃ in the range of about 1 to about 5 feet (about 0.3 to about 1.5 m), about 1 to about 4 feet (about 0.3 to about 1.2 m ) or about 1 to about 3 feet (about 0.3 to about 0.9 m). In embodiments of the invention, the shank 5 forms an angle α' less than or equal to 45, 60 or 70 degrees from the horizontal. In embodiments of the invention, the height H ₆ is equal to the sum of the height H _{1 of} the cover 1 and the height H _{3 of} the straight section 3. In the embodiments of the invention, the total height H _t equal to H ₁ +H ₂ +H ₃ +H ₄ +H ₅ is in the range about 10 to about 100 feet or more (about 3.0 to about 30.4 meters or more), about 30 to about 100 feet (about 6.0 to about 30.4 meters), or about 20 to about 100 feet (from about 6.0 to about 30.4 m).

[0039] The gas distribution system 7 may be located at least partially within the conical bottom section 2, directly above the conical bottom section 2 (for example, 5, 4, 3, 2, 1 or 0.5 feet), directly below the conical bottom section 2 (for example, 5, 4, 3, 2, 1 or 0.5 feet) or combinations thereof. For example, in the embodiment of the invention illustrated in FIG. 4, the gas distribution system 7 is located under the conical section 2 inside the section 4. In embodiments of the invention, the gas distribution system 7 is located at the lower outlet of the conical bottom section 2. In embodiments of the invention, the gas distribution system 7 includes a distributor located in the lower part (for example, in the lower 10, 15, 20, 30 or 40% of the total height H _t ) of the overflow tank 12.

[0040] In embodiments of the invention, downcomer 12 does not include a steam jacket in contact with it for supplying heat to reservoir 12. For example, downcomer 12 does not include a steam jacket typically used in conical bottom section 2.

[0041] In embodiments of the invention, a first heated treatment gas (e.g., a heated hydrocarbon treatment gas) is introduced into overflow tank 12 at a flow rate in the range of about 2500 lb/hr (1134 kg/hr) to about 20,000 lb/hr (9072 kg/hr). h), from about 2000 lb/h (907 kg/h) to about 20,000 lb/h, or from about 1000 lb/h (454 kg/h) to about 20,000 lb/h. In some such embodiments, the first heated treatment gas comprises a fuel gas. In embodiments of the invention, a first heated treatment gas (e.g., a heated hydrocarbon treatment gas) is introduced into overflow tank 12 at a flow rate in the range of about 20,000 to about 200,000 lb/hr (90,718 kg/hr), from about 10,000 lb/hr (4536 kg /h) up to about 200,000 lb/h or from about 20,000 to about 150,000 lb/h (68039 kg/h). In some such embodiments, the first heated treatment gas contains isobutane. In embodiments of the invention, the first heated treatment gas (e.g., heated hydrocarbon treatment gas) is distributed through the gas distribution system 7 at a rate (denoted as V1) in the range of about 2 to about 30 ft/min (about 0.01 to about 0.15 m/s), and a reference speed within straight section 3 (denoted as V2) in the range of about 1 to about 6 ft/min (about 0.005 to about 0.03 m/s). In embodiments of the invention, a second heated treatment gas (e.g., heated nitrogen treatment gas) is introduced into overflow tank 12 at a flow rate in the range of about 2,000 lb/hr (907.2 kg/hr) to about 20,000 lb/hr (9071.9 kg). /h), from about 5000 lb/h (2268.0 kg/h) to about 10000 lb/h (4536.0 kg/h), or from about 2000 to about 10000 lb/h. In embodiments of the invention, the second heated treatment gas (e.g., nitrogen treatment gas) is distributed through the gas distributor 7 at a rate (denoted as V1) in the range of about 2 to about 30 ft/min (about 0.01 to about 0.15 m/min). s), and a reference speed within the straight section 3 (denoted as V2) in the range of about 1 to about 6 ft/min (about 0.005 to about 0.03 m/s).

[0042] For the purpose of simplifying the following description, the polymerization system for which the overflow tank system 10 according to this disclosure may be used, as well as the operation method of the overflow tank system 10 will now be described with reference to FIG. 2, which schematically illustrates a polymerization system I, in accordance with embodiments of this invention, and FIG. 3, which schematically illustrates an integrated polymerization system II comprising an overflow tank system 10, in accordance with embodiments of this invention. The polymerization system may comprise one or more polymerization reactors 20, such as liquid phase or gas phase reactors. The polymerization system may also contain a combination of liquid phase and gas phase reactors. If the polymerization system contains multiple polymerization reactors, then the polymerization reactors may be arranged in series, in parallel, or in any other suitable combination or configuration. In polymerization reactors, one or more olefin monomers are polymerized to form a product containing polymer particles, generally referred to herein as polymer flakes. The polymer flakes may have one or more physical, rheological and/or mechanical melt properties of interest, such as density, melt index (MI), melt flow rate (MFR), copolymer or comonomer content, elastic modulus, and crystallinity. Reaction conditions, e.g., temperature, pressure, flow rate, mechanical agitation, product withdrawal, component concentrations, polymer production rate, and so on, can be selected, as is known to those skilled in the art, and with the aid of this disclosure, to achieve the desired properties of the polymer fluff. In addition to one or more olefin monomers, a catalyst is typically added to the polymerization reactor 21 to facilitate polymerization of the monomer. The catalyst may be a particle suspended in a fluid within the polymerization reactor 21 . Typically, a Phillips catalyst, Ziegler catalysts, Ziegler-Natta catalysts, metallocenes, and other well-known polyolefin catalysts, as well as co-catalysts, can be used. An example of such a catalyst is a chromium oxide catalyst containing hexavalent chromium on a silica support. An olefin-free diluent or mineral oil may be used, for example, in the preparation and/or delivery of the catalyst to the polymerization reactor 21. In addition, the diluent may be fed into the polymerization reactor 21, typically a liquid phase reactor. The diluent may be an inert hydrocarbon which is liquid under the reaction conditions, such as but not limited to isobutane, propane, n-pentane, isopentane, neopentane, n-hexane, cyclohexane, cyclopentane, methylcyclopentane, ethylcyclohexane, and similar diluents. The purpose of the diluent, in general, is to suspend the catalyst particles and the polymer in the polymerization reactor 21, for example, to form a suspension. Some polymerization processes may not use a separate diluent, such as in the case of selected polypropylene production, where the propylene monomer itself may act as a diluent. As noted above, the first treatment gas (eg, heated hydrocarbon treatment gas) used in the downcomer cleaning process may contain a diluent (eg, isobutane, isopentane).

[0043] A drive device may be present in the polymerization reactor 21 of the polymerization system. For example, within a liquid phase reactor, such as a slurry loop reactor, the impeller may create a zone of turbulent mixing in the fluid. The impeller may be driven by a motor to move the fluid, as well as any catalyst, polyolefin flakes, or other solids suspended in the fluid, through the closed loop of the reactor. Similarly, within a gas phase reactor, such as a fluidized bed or plug flow reactor, one or more paddles or agitators may be used to stir the solids within the reactor.

[0044] As discussed above, polymerization system I or integrated polymerization system II may comprise one or more polymerization reactors 20, which in turn may be of the same or different types. Furthermore, in systems with multiple reactors, the reactors may be arranged in series or in parallel. Regardless of the reactor type, a solid product is obtained from the full olefin particles, generally referred to herein as "polymer flakes". In embodiments of the invention, the polymerization reactor 21 includes a reactor within which polymerization takes place in a liquid phase. Examples of such liquid phase reactors include autoclaves, flooded boiling liquid reactors, loop slurry reactors, and so on. In embodiments of the invention, polymerization reactor 21 includes a loop slurry reactor. In embodiments of the invention, the solid polyolefin product includes polyethylene (and its copolymers). It should be understood that the methods presented are similarly applicable to other types of liquid phase reactors and polymerization processes.

[0045] A slurry loop reactor generally consists of pipe segments connected by smooth bends or elbows. In embodiments of the invention, polymerization reactor 21 may be used to carry out polymerization of polyethylene under slurry conditions, in which insoluble particles of polyolefin, such as polyethylene or polypropylene, are formed in a fluid and are suspended in suspension until they are recovered. . A drive device, such as a pump, circulates the liquid slurry in the reactor. An example of a pump is an inline axial flow pump with a pump impeller located inside the reactor to create a zone of turbulent mixing in the fluid. The impeller may also assist in propelling the fluid through the closed loop of the reactor at sufficient speed to keep solid particles, such as catalyst or produced polyolefin, in suspension in the fluid. The impeller may be driven by a motor or other traction force. In one embodiment of the invention, the polymerization reactor 21 is a loop slurry reactor that is connected to an overflow tank system 10 (e.g., reactor outlet stream line 26 is connected to an overflow tank supply line 11), such that overflow tank system 10 receives suspended contents (e.g., , stock) of the loop slurry reactor if it is necessary to reset it.

[0046] The fluid within the polymerization reactor 21 may include olefin monomers and comonomers, diluent, co catalysts (eg, triethylboron, methylalumoxane, alkyls, eg, triethylaluminum, etc.), molecular weight control agents (eg, hydrogen), and any other desired co-reagents or additives. Such olefin monomers and comonomers are generally 1-olefins having up to 10 carbon atoms per molecule and are generally unbranched near the double bond rather than at the 4-position. Examples of monomers and comonomers include ethylene, propylene, butene, 1-pentene, 1-hexene, 1-octene and 1-decene. Again, typical diluents are hydrocarbons that are inert and liquid under the reaction conditions and include, for example, isobutane, propane, n-butane, n-pentane, isopentane, neopentane, n-hexane, cyclohexane, cyclopentane, methylcyclopentane, ethylcyclohexane and similar hydrocarbons. These components are added to the interior of the polymerization reactor through inlets or pipelines at specific locations, such as those illustrated in the polymerization reactor feed line 25.

[0047] Similarly, a catalyst, for example, from the catalysts discussed above, may be added to the polymerization reactor 21 via a conduit at a suitable location, which may contain a diluent carrier. An example of a catalyst for the polymerization of ethylene monomer and the comonomers present includes chromium oxide containing hexavalent chromium (or Cr ⁺² ) on a silica support. It should be clarified that in some embodiments of the invention, the chromium in the catalyst feed enters the polyolefin plant in the form of Cr ⁺³ . This catalyst can be subjected to a process of activation with carbon monoxide (CO), which will change the valency of the activated catalyst to Cr ⁺⁶ . Subsequently, during the polymerization process in the reactor, the valency of Cr ⁺⁶ in the activated catalyst changes to Cr ⁺² due to the presence of a monomer (eg, ethylene) in the polymerization content in the polymerization reactor 21 . Advantageously, the Cr ⁺² sites in the catalyst are active for polymerization. However, it should be emphasized, as previously discussed, that different catalyst systems other than chromium systems can be used.

[0048] In General, the added components in the polymerization reactor 21, as a rule, include the fluid inside the reactor 21, within which the catalyst is a suspended particle. Reaction conditions such as temperature, pressure, and reactant concentrations are adjusted to provide the desired properties and production rate of the polyolefin in the polymerization reactor 21, to control the stability of the polymerization reactor 21, and the like. The temperature is generally kept below the level at which the polymer product goes into solution. Due to the exothermic nature of the polymerization reaction, cooling fluid can be circulated through jackets around portions of the polymerization reactor 21 to remove excess heat, thereby maintaining the temperature within the desired range, typically 150°F to 250°F (65°C to 121°C). Similarly, the pressure can be adjusted within a desired pressure range, typically 100 to 800 psi (0.6895 to 5.5158 MPa), with a typical range being 450-700 psi (3.1026-4.8263 MPa).

[0049] As the polymerization reaction proceeds in the polymerization reactor 21, the monomer (eg, ethylene) and comonomers (eg, 1-hexene) polymerize to form polyolefin (eg, polyethylene) polymers that are substantially insoluble in the fluid at a reaction temperature such thus, forming a suspension of solid particles in the medium. These polyolefin solids may be removed from the polymerization reactor 21 via a settling tank or other means, such as, but not limited to, continuous withdrawal. In post-processing as described below, the polyolefin discharged from the polymerization reactor 21 can be taken out of the slurry and purified.

[0050] The polymerization reactor effluent withdrawn from polymerization reactor 21 via polymerization reactor effluent line 26 in the polymerization system may contain polymer flakes (e.g., solid polyolefin) as well as non-polymeric components (e.g., liquid and gaseous non-product components), for example , diluent, unreacted monomer and/or comonomer, and residual catalyst. In the design of the polymerization reactor 21, in some embodiments, an outlet nozzle and conduit may be installed (eg, welded) in an outlet or hole cut in the wall of the reactor and fluidly connected to the polymerization reactor effluent line 26 . During on-line operation (e.g., in a polymerization process), the effluent from the polymerization reactor 21 via the polymerization reactor effluent line 26 is subsequently processed, for example, in the separation system 40, to separate the majority of the non-solid non-product (e.g., non-polymeric) components 48 (eg, diluent and unreacted monomer) from a solids outlet 43 (eg, solid polymer product recovery line 42) containing most of the solid product polyolefin and a minor amount of non-solid components. The non-solid non-product (e.g., non-polymeric) components exiting separation system 40 may be transferred via line 48 to recycling equipment 50, and recycling equipment 50 may be used to recycle one or more of the separated non-solid non-product components (directly or indirectly through fractionation and/or or further processing) to the polymerization reactor 21 via one or more recirculation lines 55 . One or more flash line heaters 30 (for example, three heaters: the first flash line heater 30A, the second flash line heater 30B, and the third flash line heater 30C shown in the exemplary embodiments of the invention in FIGS. 2 and 3) may be used to heat the effluent stream 26 of the polymerization reactor prior to introduction into the separator 40. In embodiments of the invention, about 5, 10, 15, 20, 25, 30 or more, 1 to 30, 5 to 30, or 10 to 30 flash line heaters or flash line heater sections may be used. While any suitable apparatus and methods known in the art may be used to separate non-product components from a solid polyolefin during normal operation (e.g., during polymerization), specific devices and methods that may be used in embodiments of this invention are will be described below with reference to FIG. 3, which schematically illustrates an integrated polymerization system II, in accordance with embodiments of this invention.

[0051] During normal operation (for example, during stationary polymerization, and not during unloading of the polymerization reactor) after passing through one or more built-in flash heaters 30 (three heaters, 30A, 30B and 30C, shown in the embodiments of the invention of FIG. 2 and 3) the effluent line 26 of the polymerization reactor 21 may be introduced into the flash chamber 32 of the separation device 40 . The built-in flash heater(s) 30A/30B/30C may surround a conduit using steam or steam condensate, for example as a heat transfer medium to provide indirect heating of the polymerization effluent stream, in the reactor effluent line 26 polymerization. Thus, the polymerization reactor effluent in the polymerization reactor effluent line 26 is heated before it is introduced into the flash chamber 32 . In addition, before the polymerization reactor effluent enters the flash chamber 32, water or other catalyst poisons may be introduced into the polymerization reactor effluent to deactivate any residual catalyst therein. Because these injected components are catalyst poisons by definition, they are typically completely removed, or at least substantially removed, from any reclaimed material (eg, monomer or diluent) recycled to the polymerization reactor 21. The flash chamber 32 is configured to separate the overhead flash gas containing most of the non-solid components of the polymerization effluent stream from the solids outlet 41 containing most of the solid polyolefin and a minor amount of non-solid components. In the flash chamber 32, most of the non-solid components of the polymerization reactor effluent stream are removed from above as vapor in the flash gas 33. In the production of polyethylene, this vapor is typically predominantly a diluent, such as isobutane or other previously mentioned diluents. This vapor may also contain unreacted monomer (for example, ethylene) and other light components, as well as unreacted comonomer (for example, 1-hexene, butene, 1-pentene, 1-octene and 1-decene) and other heavy components (for example, hexane and oligomers). In general, light components can be defined as those light components that have lower boiling points than the diluent used. Conversely, heavy components can be defined as those heavy components that have higher boiling points than the diluent. A typical approximate composition of flash gas 33 consists of 94% wt. isobutane, 5% wt. ethylene and 1% wt. other components. The level or volume of the polymer fluff may be maintained in the flash chamber 32 to provide additional residence time for the polymer fluff in the chamber 32 to facilitate separation of liquid and vapor entrained in the porous floc.

[0052] The flash gas 33 may be processed in particulate recovery equipment 34, such as, but not limited to, cyclones, bag filters, etc., where the entrained polymer fluff solids (e.g., typically fine particles or fine grained particles) are recovered and returned to the flash chamber 32 or downstream equipment, such as the purge column 42 discussed below. The flash gas 33 may also pass, for example, through the deoxygenation layer. In addition, the flash gas 33 may be transferred through line 35 and cooled or condensed in a heat exchanger 38 (eg shell and tube design). The cooled or condensed flash gas may be transferred via line 48A to recycle equipment 50 and then returned to polymerization reactor 21 via recirculation line 55 (eg, via a feed system or a fractionation system associated therewith).

[0053] In embodiments, the solids (eg, solid polyolefin) in flash chamber 32 are recovered along with minor entrained diluent (and monomer) and sent to purge column 42 via solids outlet 41. Those skilled in the art will appreciate that the solids outlet 41 may include valve configurations that allow polymer to flow down the channel while reducing the possibility of steam flowing between purge column 42 and flash chamber 32. For example, one or more rotary or cyclic valves may be located on the particulate outlet 41. In addition, one or more relatively small flake (inflow) chambers may also be located on the pipeline. In embodiments of the invention, the flocculent solids from the flash chamber 32 are discharged into the lower pressure flash chamber and the lower pressure flash gas recovered therefrom is compressed for recirculation to the polymerization reactor 21.

[0054] In embodiments of the invention, the solids outlet 41 (polyolefin flakes) that exits the flash chamber 32 is introduced into the purge column 42. The purge column 42 is configured to subject the particulate outlet to a nitrogen purge, thereby obtaining purified polymer fluff and an exhaust purge gas stream containing nitrogen and at least a portion of a minor amount of non-solid components transferred with it to the purge column (eg, diluent and/or monomer). The purpose of the purge column 42 is to remove residual hydrocarbons from the incoming solids streams and produce substantially pure polymer fluff in the purified polymer line 43. The cleaned flakes can be transferred or transferred to an extrusion/discharge system for conversion to granules and for distribution and sale as granulated polyolefin resin to the consumer, as will be known to those skilled in the art.

[0055] In the exemplary purge column system illustrated, the solid polymer product is subjected to a nitrogen purge, with nitrogen circulating through the purge column 42 to recover residual hydrocarbons through a spent purge gas stream containing nitrogen and the recovered residual hydrocarbons removed via outlet line 44.

[0056] The spent purge gas stream in exhaust line 44 may be directed through a nitrogen separator 45 configured to separate the nitrogen stream (extracted from it via nitrogen stream exhaust line 46) from the exhaust purge gas stream and thereby obtain a hydrocarbon stream , containing at least a portion of a minor amount of non-solid components (extracted from it through the outlet line 48B of the hydrocarbon stream). An outlet line 48B of the hydrocarbon stream may be fluidly connected to the recirculation line 55 via the recirculation equipment 50 . The nitrogen separator 45 may be any nitrogen separator known in the art, such as a membrane regeneration plant, a pressure swing adsorption plant, a refrigeration plant, and so on, to remove nitrogen through the nitrogen stream 46 and to discharge the separated hydrocarbon stream 48B, which can be returned to the polymerization reactor 21 via the recycling equipment 50. The nitrogen separator 45 may be known as an isobutane and nitrogen recovery unit (INRU). Moreover, fresh nitrogen 47 may be added to the nitrogen loop (e.g., added to nitrogen stream 46), taking into account losses of nitrogen in the purge column system 42. As described herein, during the discharge of the polymerization reactor, in embodiments of the invention, at least a portion of the nitrogen stream 46 produced by the nitrogen separator 45 (alone or in combination with fresh nitrogen from stream 42) may be introduced into the weir tank system 10 (e.g. via line 15A) as a second heated treatment gas (e.g., heated nitrogen treatment gas ) during the second purification step.

[0057] Those skilled in the art will appreciate that various configurations may be used in separation system 40 when recovering the diluent/monomer. For example, the solids outlet 41 from the flash chamber 32 may be routed to a different reactor (eg, a gas phase reactor) instead of the purge column 42, or to a low pressure flash chamber (eg, a second low pressure flash chamber) located between the flash chamber 32 evaporation and purge column 42). When discharged to another reactor, the catalyst poison may not be introduced upstream into the polymerization reactor effluent, and thus residual active catalysts are retained for further polymerization. In another configuration, purge column 42 may be omitted from separation system 40 and combined with a downstream extruder feed tank.

[0058] In accordance with this disclosure, the overflow tank system 10 is fluidly connected to the polymerization reactor 21, thus the stock of the polymerization reactor 21 can be transferred to the overflow tank system 10 during the unloading of the polymerization reactor. In embodiments of the invention, one or more dedicated polymerization reactor discharge lines 27 are connected to the overflow tank supply line 11 and are used to transfer the stock of the polymerization reactor to the overflow tank system 10 . Alternatively, polymerization reactor effluent line 26 is connected to overflow tank supply line 11 and is used to introduce polymerization reactor stock into overflow tank system 10 during reactor unloading. For example, as noted above, the overflow tank supply line 11 of the overflow tank system 10 illustrated in FIG. 1 may be fluidly connected to the reactor 21 of FIG. 2 through one or more dedicated reactor vent lines 27 and/or through a reactor effluent line 26 . In embodiments of the invention, overflow tank supply line 11 of overflow tank system 10 is fluidly connected to reactor effluent line 26 after at least one of one or more flash line heaters, for example, along first section 31A downstream of first flash line heater 30A. , along the second section 31B after the second flash line heater 30B and/or along the third section 31C after the third flash line heater 30C, and the contents of the polymerization reactor 21 are introduced (e.g., discharged) into the overflow tank system 10 via line 11 (for example, as indicated by the line 14 of the assignment in the embodiment of the invention in Fig. 3).

длины нагревателей линии мгновенного испарения. Например, если имеется 20 нагревателей на линии мгновенного испарения, то отводная линия 14 может соединять линию 26 отходящего потока реактора с системой 10 сливного резервуара после 13-го-15-го нагревателя линии мгновенного испарения. Например, в альтернативных вариантах осуществления изобретения отводная линия 14 соединяет по текучей среде систему 10 сливного резервуара с третьей секцией 31С линии 26 отходящего потока реактора полимеризации после третьего нагревателя 30С линии мгновенного испарения. В альтернативных вариантах осуществления изобретения отводная линия 14 соединяет по текучей среде систему 10 сливного резервуара с первой секцией 31А линии 26 отходящего потока реактора полимеризации после первого нагревателя 30А линии мгновенного испарения. Таким образом, часть циркулирующего флюида, нагретого в одном или более из одного или более нагревателей 30 линии мгновенного испарения, может быть введена в систему 10 сливного резервуара в качестве углеводородного газа обработки (например, по линии 15' нагретого газа обработки). Таким образом, нагреватель(и) линии мгновенного испарения может(гут) быть использован(ы) в качестве нагревателя 6 (например, в варианте осуществления изобретения по Фиг. 1) для нагрева флюида и получения первого нагретого газа обработки (например, нагретого углеводородного газа обработки) для ввода в систему 10 сливного резервуара.[0059] In embodiments of the invention, during the discharge of the polymerization reactor, a fluid (e.g., a diluent, e.g., isobutane) may be circulated through the polymerization reactor 21, through the flash line heater(s) 30A/30B/30C, and the separator 40 and return through the equipment 50 recycling line 55 recycling in the reactor 21 polymerization. In alternative embodiments of the invention, during the discharge of the polymerization reactor, a fluid (for example, a diluent, for example, isobutane) can be circulated through the separation device 40, the recirculation equipment 50 and the recirculation line 55, as well as through the bypass line 55' (for example, circulation through the polymerization reactor 21 missing). In some such embodiments, the stock of the polymerization reactor is transferred to the overflow tank system 10 via dedicated overflow line(s) 27 connected to the overflow line 11, and the fluid circulation mentioned above is not changed. However, in other such embodiments, weir system 10 is in fluid communication with polymerization reactor effluent line 26 downstream of at least one of one or more flash line heaters, whereby at least a portion of the fluid circulating from polymerization reactor 21 through the separation device 40 and returning to the polymerization reactor 21 through the recycling equipment 50 and the recycling line 55 during the discharge of the polymerization reactor, can be diverted to the overflow tank system 10 as the first heated treatment gas (for example, heated hydrocarbon treatment gas). For example, in the embodiment of the invention shown in FIG. 3, a bleed line 14 fluidly connects the overflow tank system 10 to the second section 31B of the polymerization reactor effluent line 26 downstream of the second flash line heater 30B. The bleed line 14 may fluidly connect the polymerization reactor effluent line 26 to the overflow tank system 10 at any location within the flash line heaters, such as approximately 2/3 or

the length of the heaters in the flash line. For example, if there are 20 heaters in the flash line, then a bleed line 14 may connect the reactor effluent line 26 to the downcomer system 10 downstream of the 13th-15th flash line heater. For example, in alternative embodiments, bleed line 14 fluidly connects overflow tank system 10 to third section 31C of polymerization reactor effluent line 26 after third flash line heater 30C. In alternative embodiments, bleed line 14 fluidly connects overflow tank system 10 to first section 31A of polymerization reactor effluent line 26 downstream of first flash line heater 30A. Thus, a portion of the circulating fluid heated in one or more of the one or more flash line heaters 30 may be introduced into the overflow tank system 10 as a hydrocarbon treatment gas (eg, through the heated treatment gas line 15'). Thus, the flash line heater(s) may be used as heater 6 (e.g., in the embodiment of FIG. 1) to heat the fluid and produce a first heated treatment gas (e.g., heated hydrocarbon gas processing) to enter the system 10 drain tank.

[0060] By using a diverted portion of the circulating fluid as a heated hydrocarbon fluid to increase the rate of heat input to the overflow tank system 10 as described herein, one can take advantage of the large capacity and heating capacity of existing flash line heaters. It is generally accepted that the polymerization reactor 21 is often used to continuously circulate a fluid (e.g., isobutane) through the flash line heaters to the separation system 40 and recirculation equipment 50, while the plant attempts to purge the overflow tank system 10 (in other words, an inert diluent, for example , isobutane, circulates through the polymerization system II during the time between the discharge of the contents of the reactor 21 into the overflow tank system 10 and the completion of the cleaning of the overflow tank system 10 so that the polymerization reactor 21 can be restarted). In accordance with embodiments of this invention, some or all of this heated fluid (for example, isobutane gas) leaving the flash line heaters can be diverted through lines 14 and 15' to the gas distribution system 7 located at the bottom (for example, below 10, 15, 20, 30, 40% of the total height H _t ) of the drain tank 12 for the first cleaning. In such embodiments, an additional heater 6 may be used to heat nitrogen to be introduced into the overflow tank 12 as a second heated process gas (e.g., through the heated process gas line 15') during the second purification step following the first purification step.

[0061] In embodiments, at least a portion of the circulating fluid (e.g., recycled isobutane) is withdrawn from recycle line 55 to polymerization reactor effluent line 26 before at least one of one or more flash line heaters 30 without passing through reactor 21 polymerization. For example, as illustrated in FIG. 3, a bypass line 55' fluidly connecting recycle line 55 to polymerization reactor effluent line 26 can be used to divert at least a portion of the fluid (eg, isobutane) circulating from recycle equipment 50 to polymerization reactor 21 during discharge. a polymerization reactor for entering at least one of one or more flash line heaters, bypassing the polymerization reactor 21 . For example, in the embodiment of the invention illustrated in FIG. 3, bypass line 55' fluidly connects recycle line 55 directly to polymerization reactor effluent line 26 before first flash line heater 30A. In alternative embodiments, bypass line 55' may fluidly connect recycle line 55 directly to first section 31A of polymerization reactor effluent line 26 after first flash line heater 30A and before second flash line heater 30B. In alternative embodiments, bypass line 55' may fluidly connect recycle line 55 directly to second section 31B of polymerization effluent line 26 after second flash line heater 30B and before third flash line heater 30C. In the event of a failure of the circulation pump (e.g. in the slurry loop reactor 21) and discharge of the contents/stock of the polymerization reactor 21 into the overflow tank system 10, the bypass line 55' can transfer fluid (e.g. isobutane) from the recirculation equipment 50 isobutane recirculation) for directly supplying isobutane to one or more of one or more flash line heaters 30A/30B/30C to provide a first heated treatment gas (e.g., isobutane gas) for the overflow tank heating process in the first purification stage.

[0062] The system and method of this invention can provide a number of advantages over conventional systems (eg, overflow tanks) and methods used to recover non-product components from polymer flakes transferred to the overflow tank during polymerization reactor discharge. Without limitation, a number of potential advantages will be described below in this document.

[0063] The downcomer and method of operation described herein provide for an increase in the heating rate in the downcomer. Another advantage is that very little additional capital equipment may be required to implement the overflow tank in accordance with embodiments of this invention, for example, due to the use of existing flash line heaters to produce heated hydrocarbon gas (e.g., isobutane) processing, such as described above. In embodiments of the invention, additional equipment includes a purge distribution system 7 within the overflow tank 12, as well as associated pipelines and valves to perform the appropriate hydraulic communications/connections described herein.

[0064] Because the first treatment gas (e.g., a hydrocarbon treatment gas) has a higher heat capacity than nitrogen and a density of about 75% of the density of nitrogen, the volumetric flow of the first treatment gas is less than that of the second treatment gas containing nitrogen, based on the same enthalpy. Accordingly, in embodiments of the invention, the time required to purge the downcomer after depressurization (e.g., the time required for the first purification step and optionally the second purification step) may be less than the time required to achieve the same heat transfer between the treatment gas, containing only nitrogen (i.e. in the absence of the first stage of purification, as described in this document). In addition, the dimensions of the overflow tank may be more accommodating for a given amount of storage of polymer flakes, and a wider range of height to diameter (e.g., H _t /D ₁ ) may be selected to meet the requirements of no fluidization, space restrictions, elevation and /or flow distributor.

[0065] In embodiments, the reduction in flow required for the same baseline enthalpy results in a reduction in the size of the overhead filter or cyclone used to separate entrained polymer particles. In embodiments of the invention, a conventional steam jacket used to heat the downcomer cone is not required, facilitating fabrication of the reservoir 12 of the downcomer system 10 and minimizing the risk of polymer melting during the downcomer purge.

[0066] Reducing the amount of nitrogen gas used to purge the sump in the manner disclosed herein can reduce the amount of nitrogen vented to the flare and a concomitant reduction in NOx emissions from the sump purge/purge process.

[0067] As noted above, in many cases, fluid (eg, isobutane) is continuously circulated through flash line heaters (eg, flash line heaters 30A/30B/30C) to separation system 40, recirculation equipment 50, recirculation line 55, and bypass line 55' (for example, bypassing the feed line 25 of the polymerization reactor), while the installation tries to clean the system 10 overflow tank. By using a diverted portion of the circulating fluid to produce a first heated treatment gas (e.g., heated hydrocarbon gas) to increase the rate of heat input to the downcomer system 10, in accordance with the embodiments of the invention described herein, the advantage of high flow capacity and heating capacity of existing flash line heaters. In accordance with embodiments of this invention, some or all of this heated fluid (for example, isobutane gas) exiting the flash line heaters can be diverted to a gas distribution system 7 located at the bottom (for example, below 10, 15, 20, 30, 40% of the total height H _t ) overflow tank 12 during the first stage of cleaning described in this document.

[0068] In embodiments, the hydrocarbon treatment gas contains fuel gas and is introduced into the downcomer system 10 as the first treatment gas in the first purification stage prior to the second purification stage, whereby a reduced total volume of nitrogen is used to purge the polymer bed in the overflow reservoir. In such embodiments, the first gas (eg, a treatment exhaust gas containing flue gas from the first scrubbing stage) may be directed directly to the flare, in embodiments of the invention. Since the fuel gas has a smaller molecular size than the non-product hydrocarbons present in the transferred polymer stock, less sorbed fuel gases on the polymer and less sorbed hydrocarbons can thus diffuse faster during the second purification step (e.g., nitrogen purge) of the overflow system 10 tank, compared to flushing the transferred stock of polymer directly/only with nitrogen (i.e., compared to flushing without the first purification step).

[0069] Because the first gas produced in the first scrubbing step can be directed to an existing hydrocarbon recovery device (e.g., INRU) of separation system 40, in embodiments of the invention, hydrocarbon losses can be reduced compared to purging the overflow tank using only nitrogen as treatment/purge gas.

[0070] The use of a first treatment gas as described herein, such as a fuel gas, can reduce the risk of purge gas condensation during the overflow tank cleaning/purging process compared to using heavier hydrocarbons as the purge gas.

EXAMPLES

[0071] After the invention has been described in general, examples are given below as specific embodiments of the invention and to demonstrate their practical application and advantages. It is understood that the examples are provided by way of illustration and are not intended to limit the description and claims in any way.

COMPARATIVE EXAMPLE 1: Nitrogen as treatment gas

[0072] As an example, the introduction of nitrogen heated to a temperature of 190°F (87.8°C) at a pressure close to atmospheric, where the nitrogen density is about 0.08 lb/ft ³ (1.28 kg/m ³ ), into the overflow tank and allowing it to cool to 90°F (32.2°C) by transferring 100°F (37.8°C) of heat and assuming a heat capacity of nitrogen of about 0.25 Btu/lb°F (1046.7 J/kg•°C), and applying a maximum speed limit of 4 ft/min (0.02 m/s) due to fluidization, the following amount of heat can be applied per unit cross-sectional area of the overflow tank through heated nitrogen :

Heat per unit area = (100°F) * (0.25 BTU/lb⋅°F) * (0.08 lb/ft ³ ) * (4 ft/minute) * (60 minutes/hour) = 480 Btu/ hour⋅ft ² (1.51 kW/m ² ).

[0073] While higher pressures and higher nitrogen mass flows can be used, this would require additional nitrogen treatment systems to recycle or flare this high nitrogen flow rate, each with different capital costs or environmental disadvantages.

EXAMPLE 1 Isobutane as a Hydrocarbon Treatment Gas

[0074] In FIG. 5 is a plot of the maximum heating rate per unit cross-sectional area versus backpressure in the overflow tank and the reduced rate. In this example, a hydrocarbon treatment gas consisting of isobutane having a temperature of 190°C is used. As seen in FIG. 5, the optimum pressure in the drain tank is about 100 psi. inch g (0.689 MPa g) when isobutane is heated to 190°F (87.8°C).

[0075] In FIG. 6 is a plot of isobutane flow versus overflow tank backpressure and reduced velocity. As seen in FIG. 6, by maintaining backpressure in the overflow tank, at low pressure, a much larger mass of isobutane can be added compared to nitrogen. In addition, this mass of isobutane has a higher heat capacity, which further increases the maximum achievable heating rate of the overflow tank.

[0076] The overflow tank described herein and the overflow tank heating method can thus be used to deliver on the order of 6000-7000 Btu/hour·ft ² (18.9-22.1 kW/m ² ) of heat into the overflow tank , which is almost 12-15 times greater than provided using only nitrogen, as described in comparative example 1 above. Assuming that heat input to the overflow tank is the dominant limit on the rate at which the overflow tank can be purged, there is a clear advantage to increasing the overflow tank heating rate using the first stage purge as described herein, resulting in a significant reduction in system purge time 10 overflow tank (and the associated minimization of the downtime of an expensive polymerization plant).

EXAMPLE 2 Fuel gas as a hydrocarbon treatment gas

[0077] Under purge conditions, the heat capacity (Cp ₁ ) of the fuel gas (e.g., 0.55 BTU/lb·°F (2302.74 J/kg·°C)) is approximately twice that of the heat capacity (Cp ₂ ) of N ₂ (0.25 BTU/lb•°F (1046.7 J/kg•°C)). The density (ρ ₁ ) of the fuel gas (for example, 0.12 lb/ft ³ (1.92 kg/m ³ )) is 75% of the density (ρ ₁ ) N ₂ (0.16 lb/ft ³ (2.56 kg / m ³ )). Therefore, the fuel gas volume flow (V ₁ =(Cp ₂ *ρ ₂ )/(Cp ₁ *ρ ₁ ) is only about 66% of the N ₂ volume flow (V ₂ ) at the same base enthalpy value. Accordingly, the fuel gas can be used as a hydrocarbon treatment gas in the first stage purification process to similarly reduce the purification time for the downcomer system 10, in accordance with embodiments of this invention.

ADDITIONAL DESCRIPTION

[0078] The specific embodiments of the invention described above are illustrative only, as the invention may be modified and practiced in various but equivalent ways that will be apparent to those skilled in the art, who can take advantage of the ideas given in this document. In addition, no restrictions are provided for the details of construction given in this document, other than those described in the following claims. Therefore, it is obvious that the specific illustrative embodiments of the invention described above may be changed or modified, and all such variations are contemplated within the scope and essence of this invention. Alternative embodiments of the invention that result from combining, integrating and/or eliminating features of the embodiment(s) of the invention are also within the scope of the invention. Although the compositions and methods are described in broader terms "having", "comprising" or "comprising" various components or steps, these compositions and methods may also "essentially consist of" or "consist of" various components and steps. The use of the term "optionally" in relation to any element of the claims means that the specified element is necessary or, alternatively, the specified element is not necessary, and both alternatives are within the scope of the claims.

[0079] The numbers and ranges described above may vary by some amount. In each case where a numeric range with a lower limit and an upper limit is disclosed, any number and any included range falling within said range are specifically disclosed. In particular, each range of values (in the form "from about a to about b" or, equivalently, "from about a to b", or equivalently, "from about a-b") described in this document, should understood as describing each number and range included in the wider range of values. Also, the terms in the claims have their simple, ordinary meaning, unless otherwise expressly and clearly defined by the patent owner. In addition, the use in the claims of definitions in the singular in this document refers to one or more than one defined element. If there is any conflict in the use of a word or term in this specification and one or more patent or other documents, then definitions that are consistent with this description shall be adopted.

[0080] Embodiments of the invention disclosed herein include:

[0081] A: A method of operating an overflow tank of a polymer production process, said method comprising: transferring all or part of the polymerization reactor contents to an overflow tank, the reactor contents including solid polymer and liquid and gaseous non-product components; and removing at least a portion of the liquid and gaseous non-product components from the overflow reservoir by: depressurizing the overflow reservoir, whereby a flash gas containing a first portion of at least a portion of the liquid and gaseous non-product components is removed from the overflow reservoir; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first a gas containing a second portion of at least a portion of the liquid and gaseous non-product components from the overflow tank during the first purification step; and subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas containing a third of at least a portion of liquid and gaseous non-product components from drain tank during the second stage of cleaning.

[0082] B: A system comprising: an overflow tank into which all or part of the contents of the polymerization reactor can be transferred during unloading of the polymerization reactor in a polymer production process, the overflow tank comprising: a gas distribution system configured to distribute the treatment gas introduced into it along the inlet line of the processing gas, essentially uniformly across the cross section of the overflow tank, while the gas distribution system is located in the lower part of the overflow tank; a heater configured to raise the temperature of the treatment gas to the temperature of the treatment gas; a helmet pipeline connecting the drain tank with a torch in a fluid medium; and a ventilation filter on the helmet conduit, wherein the ventilation filter is configured to trap entrained polymer particles in the gas passing through the helmet conduit.

[0083] C: A method for the production of polyolefins, comprising:

(i) during normal operation: polymerizing a polymerization feed containing a monomer, a diluent and optionally a comonomer in the presence of a polymerization catalyst to form a polymerization effluent containing a solid polymer and liquid and gaseous non-product components; passing the polymerization reactor effluent through one or more flash line heaters configured to indirectly heat the polymerization reactor effluent; separating one or more non-product components from the polymerization reactor effluent using a separating device; and recycling at least one of one or more of the separated non-product components to the polymerization reactor through a recycle line, and (ii) in the process of unloading the polymerization reactor: transferring all or part of the contents of the polymerization reactor to an overflow tank, wherein the contents of the reactor include a solid polymer, and also liquid and gaseous non-food components; and removing at least a portion of the non-product components from the overflow reservoir by: depressurizing the overflow reservoir, whereby a flash gas containing a first portion of at least a portion of the non-product components is removed from the overflow reservoir; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first gas containing the second part of at least part of the non-product components from the drain tank during the first stage of purification; and subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas containing a third of at least a portion of non-product components from the overflow tank into during the second purification step.

[0084] Each of embodiments A, B, and C may have one or more of the following additional elements: Element 1: wherein the first heated treatment gas introduced into the downcomer during the first purification stage contains one or more hydrocarbons having from one to five carbon atoms (hydrocarbons C1-C5). Element 2: wherein the first heated treatment gas introduced into the overflow tank during the first purification step has a temperature in the range of about 85 to about 95, about 80 to about 90, or about 90 to about 95% of the melting point of the solid polymer. Element 3: wherein the temperature of the first purification step is in the range of about 85 to about 95, about 80 to about 90, or about 90 to about 95% of the melting point of the solid polymer. Element 4: wherein the first heated treatment gas contains isobutane, isopentane, fuel gas, propane, propylene, or a combination thereof. Element 5: in which the first heated treatment gas is introduced into the bottom of the overflow tank. Element 6: wherein the first heated treatment gas is introduced into the overflow reservoir through a gas distribution system configured to distribute the first heated treatment gas substantially evenly over the cross-sectional area of the overflow reservoir. Element 7: wherein the gas distribution system comprises a fluidized bed grid plate, a distributor, or a combination thereof. Element 8: further comprising introducing the first heated treatment gas into the overflow tank at a reduced rate that is below the minimum fluidization rate of the solid polymer therein. Element 9: additionally including maintaining back pressure in the drain tank during the first stage of cleaning. Element 10: in which, during the first stage of cleaning, the heating rate per cross-sectional area of the overflow tank exceeds or is about 5000 BTU/hour·ft ² (15.76 kW/m ² ) due to the introduction of the first heated treatment gas. Element 11: further comprising selecting a flow rate of the first heated treatment gas, a temperature of the first heated treatment gas, a back pressure in the overflow tank, or a combination thereof to minimize the time of the first stage of purification, wherein the time of the first stage of purification is the duration of the first stage of purification. Element 12: wherein the temperature of the first purification stage is reached in a first purification stage time of less than or equal to about 10 hours, wherein the first purification stage time is the duration of the first purification stage. Element 13: wherein the time required to extract at least a portion of the liquid and gaseous non-product components from the polymer flakes is less than or equal to approximately 80% of the time required to extract at least the same portion of the liquid and gaseous non-product components from the same solid polymer in the same way, with the difference that only a purification step using a heated treatment gas containing mainly nitrogen is used, and not two purification stages in which the first purification stage uses a first heated treatment gas containing mainly one or more hydrocarbons. Element 14: additionally including flaring the first gas, wherein said method produces an amount of NOx emissions from flaring that is less than or equal to the amount of NOx emissions produced by the same method, with the difference that one purification stage using heated gas is used treatment containing mainly nitrogen, and not two stages of purification, in which the first stage of purification uses a first heated treatment gas containing mainly one or more hydrocarbons. Element 15: wherein the polymer production process includes an isobutane nitrogen recovery unit (INRU), and wherein at least a portion of the nitrogen introduced into the overflow tank via the second treatment gas includes nitrogen recovered from INRU. Element 16: further comprising introducing a second gas into an INRU or other separation device configured to separate nitrogen from the second gas. Element 17: in which the overflow tank is a cylindrical tank having a conical bottom section. Element 18: in which the gas distribution system is at least partially inside the conical bottom section, directly above the conical bottom section, directly below the conical bottom section, or a combination of both. Element 19: in which the overflow tank does not contain a steam jacket in contact with the conical bottom section. Element 20: in which the conical bottom section forms an angle of 45, 60, or 70 degrees or less from the horizontal. Element 21: further comprising: a polymerization reactor configured to polymerize the monomer in the presence of a polymerization catalyst to produce a polymerization effluent containing a solid polymer and non-solid components; a polymerization reactor effluent line configured to divert a polymerization effluent from the polymerization reactor; one or more flash line heaters located proximate the polymerization reactor effluent and configured to indirectly heat the polymerization reactor effluent; a separating device configured to receive the heated effluent stream of the polymerization reactor, separate the majority of the non-solid components from the solid polymer, and allow for the release of solid particles comprising the majority of the solid polymer and a minor amount of the non-solid components; as well as recycling equipment configured to recycle one or more separated non-solid components to the polymerization reactor through a recycling line, and the overflow tank is fluidly connected to the polymerization reactor, so that the stock of the polymerization reactor can be transferred to the overflow tank during the unloading of the polymerization reactor. . Element 22: wherein the overflow tank is in fluid communication with the polymerization reactor effluent line, downstream of at least one of the one or more flash line heaters, whereby at least a portion of the fluid circulating from the polymerization reactor through the separation device and returned to polymerization reactor through the recycling equipment in the discharge process from the polymerization reactor, can be diverted to the overflow tank as a treatment gas. Element 23: further comprising a bypass line fluidly connecting the recirculation line to the polymerization reactor effluent, whereby at least a portion of the fluid returned from the recirculation equipment to the polymerization reactor during unloading of the polymerization reactor can be diverted to introduce at least in one of the one or more heaters of the flash line without passing through the polymerization reactor, and the diverted part can be introduced into the overflow tank as a treatment gas. Element 24: in which the separation device includes: a flash chamber configured to receive and separate the heated polymerization reactor effluent into a flash gas containing a majority of non-solid components, and a solids outlet containing a majority of the solid polyolefin and a minor amount of non-solid components ; a purge column configured to receive a solids outlet and subject the particulates outlet to a nitrogen purge, thereby obtaining a purified solid polymer and an exhaust purge gas stream containing nitrogen and at least a portion of a minor amount of non-solid components; and a nitrogen separator configured to receive and separate the exhaust purge gas stream into a nitrogen stream extracted from it through the outlet line of the nitrogen stream, and a hydrocarbon stream containing at least a portion of a small amount of non-solid components extracted from it through the outlet line of the hydrocarbon stream , wherein the recirculation line is fluidly connected to an outlet hydrocarbon flow line. Element 25: further comprising a line fluidly connecting the nitrogen flow outlet line to the downcomer, whereby at least a portion of the nitrogen stream can be introduced into the downcomer as a treatment gas. Element 26: further comprising, during the discharge of the polymerization reactor (ii), circulation of fluid from the polymerization reactor through one or more flash line heaters, a separation device and a recirculation line back to the polymerization reactor, as well as diverting at least a portion of the fluid to an overflow tank as the first heated treatment gas. Element 27: wherein at least a portion of the fluid is diverted to an overflow tank downstream of at least one of the one or more flash line heaters. Element 28: wherein at least a portion of the fluid is withdrawn from the recirculation line to an overflow tank without passing through the polymerization reactor. Element 29: wherein separating one or more non-product components from the polymerization reactor effluent stream through the separating device further comprises: separating, in the flash chamber, the polymerization reactor effluent stream into an overhead flash gas containing a major portion of the non-product components to allow a particulate discharge containing a large part of the solid polyolefin and a small amount of non-product components; subjecting the particulate outlet to a purge of nitrogen in a purge column, thereby separating the purified polymer fluff from an exhaust purge gas stream containing nitrogen and at least a portion of a minor amount of non-product components; and separating in the nitrogen separator the nitrogen stream from the exhaust purge gas stream to obtain a hydrocarbon stream containing at least a portion of a minor amount of non-solid components, wherein one or more separated non-product components recycled to the polymerization reactor contain at least a portion of the hydrocarbon stream. Element 30: wherein at least a portion of the nitrogen introduced into the overflow tank as the second heated treatment gas during the second purification step in the discharge process (ii) of the polymerization reactor contains nitrogen separated in a nitrogen separator from the waste purge gas stream and/or from another nitrogen-containing stream. Element 31: wherein the other nitrogen-containing stream contains the second gas. Element 32: wherein the nitrogen separator comprises a membrane recovery unit, a pressure swing adsorption unit, a refrigeration unit, or a combination thereof. Element 33: in which the nitrogen separator contains an isobutane and nitrogen recovery unit (INRU).

[0085] While preferred embodiments of the present invention have been shown and described, modifications may be made by one skilled in the art without deviating from the spirit and ideas of the present invention. The embodiments of the invention described herein are illustrative only and are not intended to be limiting. Numerous variations and modifications of the invention described herein are possible and are within the scope of this invention.

[0086] Numerous other modifications, equivalents, and alternatives will become apparent to those skilled in the art once the invention described above has been fully appreciated. It is intended that the following claims be interpreted to cover all such modifications, equivalents and alternatives, where applicable. Accordingly, the scope of legal protection is not limited to the description set forth above, but is limited only by the claims below, and this scope includes all equivalents of the subject matter in the claims. All claims without exception are included in the description as an embodiment of the present invention. Therefore, the claims are a further description and are in addition to the detailed description of the present invention. The disclosures of all patents, patent applications and publications mentioned in this document are incorporated herein by reference.

Claims (45)

1. A method for operating an overflow tank of a polymer production process, including: transferring all or part of the contents of the polymerization reactor to the overflow tank, and the contents of the reactor includes a solid polymer, as well as liquid and gaseous non-product components; and removing at least a portion of the liquid and gaseous non-product components from the discharge reservoir by: depressurizing the overflow reservoir, whereby a flash gas containing a first portion of at least a portion of the liquid and gaseous non-product components is removed from the overflow reservoir; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first a gas containing a second portion of at least a portion of the liquid and gaseous non-product components from the overflow tank during the first purification step; as well as subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank and extracting a second gas containing a third of at least a portion of liquid and gaseous non-product components from the overflow tank during the second purification step. 2. The method according to claim 1, characterized in that the first heated treatment gas introduced into the overflow tank during the first purification stage contains one or more hydrocarbons having from one to five carbon atoms (C1-C5 hydrocarbons). 3. The method of claim. 1, characterized in that the first heated treatment gas introduced into the overflow tank during the first stage of purification has a temperature that is in the range from about 85 to about 95% of the melting point of the solid polymer, and the temperature of the first the purification step is in the range of about 85 to about 95% of the melting point of the solid polymer, or both. 4. The method of claim 1, wherein the first heated treatment gas comprises isobutane, isopentane, fuel gas, propane, propylene, or a combination thereof. 5. The method of claim. 1, characterized in that the first heated treatment gas is introduced into the lower part of the overflow tank. 6. The method of claim 5, wherein the first heated treatment gas is introduced into the overflow reservoir through a gas distribution system configured to distribute the first heated treatment gas substantially evenly over the cross-sectional area of the overflow reservoir. 7. The method of claim 1, further comprising maintaining backpressure in the overflow reservoir during the first cleaning step. 8. The method according to claim 1, characterized in that during the first stage of cleaning, the heating rate per cross-sectional area of the drain tank exceeds or is about 5000 Btu / h⋅ft ² (15.76 kW / m ² ) due to the introduction of the first heated processing gas. 9. A system for carrying out the method according to any one of the preceding claims, comprising: an overflow tank into which all or part of the contents of the polymerization reactor may be transferred during discharge from the polymerization reactor during polymer production, the overflow tank comprising: a gas distribution system configured to distribute the treatment gas introduced therein through the treatment gas inlet line substantially uniformly across the cross section of the downcomer, the gas distribution system being located at the bottom of the downcomer; a heater configured to raise the temperature of the treatment gas to the temperature of the treatment gas; a helmet pipeline connecting the drain tank with a torch in a fluid medium; as well as a ventilation filter on the helmet conduit, wherein the ventilation filter is configured to trap entrained polymer particles in the gas passing through the helmet conduit. 10. The system according to claim 9, characterized in that the drain tank is a cylindrical container having a conical bottom section. 11. The system according to claim. 10, characterized in that the overflow tank does not contain a steam jacket in contact with the section of the conical bottom. 12. The system according to claim 9, further comprising: a polymerization reactor configured to polymerize the monomer in the presence of a polymerization catalyst to produce a polymerization effluent containing a solid polymer and non-solid components; a polymerization reactor effluent line configured to withdraw a polymerization effluent from the polymerization reactor; one or more flash line heaters configured to indirectly heat the polymerization reactor effluent; a separating device configured to receive the heated effluent stream of the polymerization reactor, separate most of the non-solid components from the solid polymer, and allow the release of solid particles containing most of the solid polymer and a minor amount of non-solid components; as well as recycling equipment configured to recycle one or more separated non-solid components to the polymerization reactor via a recycling line, wherein the overflow tank is fluidly connected to the polymerization reactor, so that the stock of the polymerization reactor can be transferred to the overflow tank during unloading of the polymerization reactor. 13. The system of claim. 12, characterized in that the overflow tank is connected in fluid with the polymerization reactor effluent line, downstream of at least one of the one or more flash line heaters, whereby at least a portion of the fluid circulating from the reactor polymerization through the separation device and returned to the polymerization reactor through the recycling equipment in the process of discharge from the polymerization reactor, can be diverted to the overflow tank as a treatment gas. 14. The system of claim 12, further comprising a bypass line fluidly connecting the recirculation line to the polymerization reactor effluent, whereby at least a portion of the fluid returned from the recirculation equipment to the polymerization reactor during unloading of the polymerization reactor can be diverted for introducing into at least one of one or more heaters of the flash line without passing through the polymerization reactor, and the withdrawn part can be introduced into the overflow tank as a treatment gas. 15. Method for the production of polyolefins, including: (i) during normal operation: polymerizing the polymerization feedstock containing the monomer, diluent and optionally comonomer in the presence of a polymerization catalyst to form a polymerization effluent containing a solid polymer and liquid and gaseous non-product components; passing the polymerization reactor effluent through one or more flash line heaters configured to indirectly heat the polymerization reactor effluent; separating one or more non-product components from the polymerization reactor effluent stream through a separation device and recycling at least one of the one or more separated non-product components to the polymerization reactor via a recycling line; and (ii) during the discharge of the polymerization reactor: transferring all or part of the contents of the polymerization reactor to the overflow tank, and the contents of the reactor includes a solid polymer, as well as liquid and gaseous non-product components; and removing at least a portion of the non-product components from the overflow tank by: reducing the pressure in the overflow tank, whereby the flash gas containing the first part of at least part of the non-product components is removed from the overflow tank; subjecting the solid polymer to a first purification step, which includes heating the solid polymer by introducing a first heated treatment gas containing primarily one or more hydrocarbons into an overflow tank until the temperature of the solid polymer in the first purification step is reached, and withdrawing the first gas containing the second part of at least part of the non-product components from the drain tank during the first stage of purification; as well as subjecting the solid polymer to a second purification step, comprising purging the solid polymer by introducing a second heated treatment gas containing mainly nitrogen into the overflow tank, and extracting a second gas containing a third of at least a portion of non-product components from the overflow tank in the process of the second purification steps. 16. The method of claim 15, further comprising, in the process of unloading the polymerization reactor (ii), circulating fluid from the polymerization reactor through one or more flash line heaters, a separation device, and a recirculation line back to the polymerization reactor, and diverting at least part of the fluid into the overflow tank as the first heated treatment gas. 17. The method of claim. 16, characterized in that at least part of the fluid is discharged into the overflow tank after at least one of the one or more flash line heaters. 18. The method of claim. 16, characterized in that at least part of the fluid is removed from the recirculation line in the overflow tank without passing through the polymerization reactor.

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