MXPA00011306A - Continuous slurry polymerization volatile removal - Google Patents

Abstract

A process/apparatus is disclosed for continuously separating a liquid medium comprising diluent and unreacted monomers from a polymerization effluent comprising diluent, unreacted monomers and polymer solids,comprising a continuous discharge of the polymerization effluent from a slurry reactor through a discharge valve and transfer conduit into a first intermediate pressure flash tank with a conical bottom defined by substantially straight sides inclined at an angle to that of horizontal equal to or greater than the angle of slide of the slurry/polymer solids and an exit seal chamber of such diameter (d) and length (l) as to maintain a desired volume of concentrated polymer solids/slurry in the exit seal chamber such as to form a pressure seal while continuously discharging a plug flow of concentrated polymer solids/slurry bottom product of said first flash tank from the exit seal chamber through a seal chamber exit reducer with inclined sides defined by substantially straight sides inclined at an angle to that of horizontal equal to or greater than the angle of slide of the polymer solids which remain after removal of about 50 to 100%of the inert diluent therefrom to a second flash tank at a lower pressure.

Description

REMOVAL OF VOLATILES IN CONTINUOUS POLYMERIZATION IN GROUT # Field of the Invention The present invention relates to an apparatus for continuously separating polymer solids from a liquid medium comprising an inert diluent and unreacted monomers in a slurry polymerization process. In particular, the present invention relates to an apparatus for continuously separating polymer solids from a liquid medium, drying the polymer, and recovering the diluent and the unreacted monomers with a reduction in compression necessary for the condensation of diluting vapor in liquid diluent. for re-use in the polymerization process. In another aspect, the invention relates to a method for continuously separating polymer solids from a liquid medium. In particular, the invention relates to a method for continuously separating polymer solids from a liquid medium, drying the polymer, and recovering the inert diluent and unreacted monomers for reuse in the polymerization process. BACKGROUND OF THE INVENTION In many polymerization processes for the production of polymers, a polymerization effluent is formed which is a slurry of particulate polymer solids, suspended in a liquid medium, ordinarily the reaction diluent and "" "Unreacted monomers." A typical example of such processes is disclosed in U.S. Patent No. 2,285,721 to Hogan and Bank, the disclosure of which is incorporated herein by reference. • reference. Although the polymerization processes described in the Hogan document employ a catalyst comprising chromium oxide and a support, the present invention is applicable to any process that produces an effluent comprising a slurry of polymeric solids in suspended particles in a liquid medium that It comprises a diluent and monomer without reaction # nar. Such reaction processes include those that have been known in the art as particle polymerizations. In most commercial-scale operations, it is desirable to separate the polymer and the liquid medium comprising a Inert diluent and unreacted monomers such that the liquid medium is not exposed to contamination so that the liquid medium can be recycled to the polymerization zone with minimal purification, if at all. One particularly favored technique that has been used so far is that disclosed in US Pat. No. 3,152,872, to Scoggin et al., More particularly the embodiment illustrated in conjunction with FIG. 2 of that patent. In such processes, the reaction diluent, dissolved monomers, and catalyst are circulated in a closed loop reactor 5 where the polymerization reaction pressure is about 100 to 700 psi absolute. The solid polymer produced is also circulated in the reactor. A polymer slurry and liquid medium is collected on one or more settlement legs • from the closed-loop reactor of slurry from which slurry is periodically discharged to a flash chamber where the mixture is drained at a low pressure, such as about 20 psi absolute. Although the flash results in substantially complete removal of the liquid medium from the polymer, it is necessary to re-compress the vaporized polymerization diluent (i.e. • isobutane) in order to condense the recovered diluent into a liquid form suitable for recycling as a liquid diluent to the polymerization zone. The cost of the compression equipment and the energy required for its operation often correspond to a considerable portion of the expenses involved in the production of the polymer. Some polymerization processes distill the liquefied diluent before recycling it to the reactor. The purpose of the distillation is the removal of monomers and contaminants from the light end. The distilled liquid diluent is then passed through a treatment bed to remove poisons from the catalyst and then to the reactor. The equipment and the energy costs for distillation and treatment can be a considerable portion of the cost of producing the polymer. In a commercial scale operation, it is desirable to liquefy the vapors of the diluent at minimum cost. One such technique used so far is disclosed in U.S. Patent No. 4,424,341, to Hanson and Sherk, in which an intermediate pressure flash step removes a considerable portion of the diluent at a temperature and pressure such that this portion Drain from the diluent can be liquefied by heat exchange rather than by a more expensive compression procedure. SUMMARY OF THE INVENTION The present invention relates to an apparatus for continuously separating polymeric solids from a liquid medium comprising an inert diluent and unreacted monomers. In another aspect, the invention relates to an apparatus for continuously separating polymer solids from a liquid medium, drying the polymer, and recovering the unreacted diluent and monomers with a reduction in compression necessary for vapor condensation from the diluent in liquid diluent to re-use in a polymerization process. In another aspect, the invention relates to a method for continuously separating polymer solids from a liquid medium. In another aspect, the invention relates to a method for continuously separating polymer solids from a liquid medium, drying the polymer, and recovering the inert diluent and unreacted monomers for re-use in a polymerization process. According to the present invention, an apparatus for continuously recovering polymer solids from a polymerization effluent comprising a slurry of said concentrated polymer / slurry to a second flash tank is provided, wherein the pressure of said second flash tank and the temperature of the concentrated polymer / slurry solids are such that essentially all of the inert diluent and / or monomer if remaining reactants are vaporized and withdrawn in the head for compression and heat exchange condensation and the polymer solids are discharged from the bottom of said second tank. flash for additional processing or storage. The invention also provides a method for the continuous removal of a stream of polymerization effluent from a slurry reactor through a discharge valve; increasing the heat content of the polymerization effluent during its transit through said first transfer conduit at a temperature below the melting point of the polymer while continuously communicating the polymerization effluent to a first flash tank having a substantially defined bottom by sides straight inclined at an angle with the horizontal equal to or greater than the sliding angle of the concentrated polymeric / slurry solids; continuously vaporize from about 50 to about 100% of the liquid medium in said first heated flask tank to yield concentrated polymeric / slurry solids and a vapor stream at a temperature and pressure such that the inert diluent content of said vapor is condensable, without compression, by heat exchange with a fluid having a temperature in the range of about 65 to about 135 * F; continuously discharging the concentrated polymeric / slurry solids from said first flash tank to an outlet seal chamber of said first flash tank of a length (1) and a diameter (d) such that a volume of polymeric solids / slurry concentrates is continuously maintained so as to form a pressure seal in said outlet seal chamber of said first flash tank; continuously discharging the concentrated polymeric / slurry solids from said outlet seal chamber of said first flash tank through a seal chamber outlet reducer defined by substantially straight sides inclined at an angle with the horizontal equal to or greater than the angle of sliding of the polymeric solids that remain after the removal of around 50 to 100% of the inert diluent thereof; communicating a continuous plug flow of polymeric solids / slurry concentrates from said outlet seal chamber of said first flashing tank through said seal chamber outlet reducer to a second transfer conduit communicating said plug flow continuous polymer solids / slurry to a second flash tank; and continuously vaporizing essentially all of the inert diluent and / or unreacted monomer remaining in a second flash tank operated at a lower pressure than said first flash tank; condensing the vaporized inert diluent and / or unreacted monomer of said second flash tank by compression and heat exchange; and continuously discharging the essentially dry polymer slurry from said second flash tank for further processing or storage. The present invention also relates to an apparatus for capturing a higher weight percentage of polymer solids from a slurry circulating in a closed loop reactor than the weight percent solids in the circulating slurry. The apparatus includes a conduit having a first end, wherein said first end extends a distance to the closed loop reactor. The conduit also has portions defining an opening where said opening is positioned relative to the direction of the circulating slurry. Desirably, the opening may be facing the direction of flow of the circulating slurry. Additionally, a portion of the conduit may extend out of the closed loop reactor to discharge, continuously or otherwise, the polymer solids of the closed loop reactor. The present invention also provides a process for capturing a higher percentage by weight polymeric solids of a slurry circulating in a closed-loop reactor than the weight percentage of polymer solids in the circulating slurry. This process includes the step of extending a distance to the closed-loop reactor a conduit having portions defining an opening, wherein said opening extends toward the circulating slurry. Additionally, this process may include the step of discharging, continuously or otherwise, the polymer solids of the closed loop reactor through a portion of the conduit extending • out of the closed loop reactor. The present invention also provides an apparatus for purging polymeric solids from a conduit connected to a closed loop reactor and in fluid communication with the closed loop reactor. This apparatus includes a sensor, a first valve in fluid communication with the conduit, a second one • valve placed between a first inert diluent and the conduit, where the first inert diluent is in fluid communication with the conduit between the closed-loop reactor and the first valve. In response to a signal produced by the sensor, the first valve is closed and the second valve is opened, allowing the first inert diluent to enter the conduit in sufficient quantities and under sufficient pressure to purge polymeric solids from the conduit. This apparatus may further include a third valve positioned between a second inert diluent and the conduit, wherein the second inert diluent is in fluid communication with the conduit between the closed-loop reactor and the first valve. In this way, when the first valve is opened and the second valve is closed, the third valve is opened, allowing the second inert diluent to enter the conduit. The present invention also provides a process for purging polymer solids from a conduit connected to a closed loop reactor and in fluid communication with the closed loop reactor. This process includes the steps of (1) closing a first valve in response to a first signal from a first sensor, where the first valve is connected to and in fluid communication with the conduit, (2) opening a second valve in response to a second signal from a second sensor, where the second valve is in fluid communication between a first inert diluent and the conduit, and where the first inert diluent is in fluid communication with the conduit between the closed-loop reactor and the first valve, and (3) flowing sufficient quantities of the first inert diluent under sufficient pressure into the conduit to purge polymeric solids from the conduit. In this process, the first and second sensors can be a common sensor and the first and second signals can be a common signal. The present invention also provides an apparatus for returning fine particles to a polymerization slurry in a closed loop reactor. The apparatus includes a discharge valve for discharging a portion of the polymerization slurry from the closed-loop reactor to a first transfer conduit. The first transfer conduit communicates the polymerization slurry to a first flash tank. The first flash tank converts a portion of the polymerization slurry into a first fluid, such as a vapor. The first fluid includes a portion of the diluent and the fine particles of the polymerization slurry. A second transfer conduit communicates the first fluid to a first separator • cyclonic. The first cyclonic separator converts a portion of the first fluid into a second fluid, such as a vapor. The second fluid includes a portion of the diluent and the fine particles. A third transfer conduit communicates the second fluid to a heat exchanger. The heat exchanger converts the second fluid into a liquid comprising the & diluent and fine particles. A fourth transfer conduit returns the liquid to the polymerization slurry in the closed loop reactor. The apparatus may also include a heater of the first transfer conduit for exchange between the heater of the first transfer conduit and the polymerization slurry. The present invention also provides a process for returning fine particles to a polymerization slurry in a closed loop reactor. The process includes (i) unloading a portion of the polymerization slurry from the 0-loop reactor, (ii) communicating the discharge polymerization slurry to a first flash tank, (iii) converting in the flash tank a portion of the polymerization slurry in a first fluid, the first fluid comprising a thinner and the fine particles, (iv) communicating the first fluid of the first flash tank to a first cyclone separator, (v) converting in the cyclone separator a portion of the first fluid in a second fluid comprising the diluent and the fine particles, (vi) communicating the second fluid to a heat exchanger, • (vii) converting in the heat exchanger the second fluid in a liquid comprising the diluent and the fine particles, and (viii) returning the liquid to the polymerization slurry in the closed loop reactor. The present invention further provides an apparatus and a process for producing polymer from a polymerization slurry in a closed-loop reactor operating at a space-time yield greater than 2.8 lbs / hr-gal. In this case, the polymer is formed in the polymerization slurry, which includes a liquid and solid medium. The polymerization slurry is discharged into a first transfer conduit. The grout Polymerization is referred to as a polymerization effluent upon leaving the closed loop reactor. The polymerization effluent is heated in the first transfer conduit to a temperature below the melting temperature of the polymer solids. The heated polymerization effluent 0 is communicated through said first transfer conduit to a first flash tank. In the first flash tank, it vaporizes from about 50 to about 100% of the liquid medium. The steam is condensed by heat exchange. The polymeric solids are discharged from the first flash tank 5 to a second flash tank through a seal chamber of sufficient dimensions such that a volume of polymer solids is maintained in said seal chamber sufficient to maintain a pressure seal. Polymer solids are • then communicated to a second flash tank. In the second flash tank, the polymer solids are exposed to a pressure reduction, from a higher pressure in the first flash tank to a lower pressure in said second flash tank. The polymer solids are then discharged from the second flash tank. Additionally, the $ percentage by weight of solids in the polymerization slurry can be greater than 47%. The closed loop reactor can be operated at a total distance from the recirculating pumping head / reactor of more than 0.15 ft / ft. The closed loop reactor can also be operated with a recirculating pumping head greater than or equal to 200 ft and having more than eight vertical legs, desirably between 10 and 16 vertical legs, more desirably between 10 and 12 vertical legs, most desirably 12 vertical legs. The volume of polymerization slurry in the closed-loop reactor can be greater than 20,000 gallons. An object of the present invention is to provide both an apparatus and a method for the continuous flash drying in two stages of the polymer solids after the continuous removal of the polymerization effluent comprising polymeric solids and liquid medium comprising inert diluent and unreacted monomers from a slurry reactor through a point discharge valve, a continuous control of solids level in the outlet seal chamber of the first flash tank which provides a pressure seal there allowing said The first tank operates under a substantially greater pressure than said second flash tank while the polymer solids are continuously discharged through the outlet reducer of the seal chamber to the second transfer conduit and additionally to the second flash tank, which eliminates the plugging in the first flash tank and the continuous liquefaction of around 50 to about 100% of the inert diluent vapor by exchange of heat rather than compression. Another object of the invention is to eliminate the need for a settling leg in the slurry reactor and the intermittent high pressure pulse in the slurry reactor caused by periodic discharges of the contents of the settling leg. Another objective of the present invention is to improve safety, eliminating the possibility of plugging in a settling leg. Another object of the invention is to eliminate plugging in the downstream equipment of a discharge valve. In a settling leg of a polymerization reactor, the polymerization continues and the heat of reaction additionally heats the liquid medium and there is a potential for some of the polymer solids to dissolve or melt together. When leaving the discharge valve the content of the exit of the settling leg, the pressure drop causes the flash of something of the liquid medium, which results in cooling the remaining liquid medium, causing the dissolved polymer to precipitate, which tends to plug the equipment downstream. The present invention, which eliminates the need for a settling foot, also eliminates this potential for plugging downstream equipment by preventing the initial dissolution or melting of the polymer solids. Another object of the present invention is to increase the reactor efficiency by the use of continuous discharge and increased concentrations of ethylene in the liquid medium, for example greater than or equal to 4% by weight at the outlet of the reactor, desirably from 4 to 8% by weight, still more desirable from 5 to 7% by weight. Settling legs limit ethylene concentrations due to an increased tendency to plug downstream equipment caused by accelerated reaction within the settling foot. A continuous flow of polymerization effluent slurry allows ethylene concentrations to be limited only by the solubility of the ethylene in the liquid diluent in the reactor, thereby increasing the specific reaction rate for the polymerization and increasing the yield of the reactor. Another object of the present invention is to increase the weight percentage (% by weight) of polymer solids in the polymerization slurry circulating in the polymerization zone in the closed loop reactor. Desirably, the weight percent polymeric solids in the polymerization slurry is greater than 45, more desirably from 45 to 65, still more desirably from 50 to 65, and most desirably from 55 to 65%. Another objective of the present invention is to increase the space time (STY) performance, expressed in terms of pounds per hour-gallon (Ibs / hr-gal). Desirably, the STY is greater than 2.6, more desirably from 2.6 to 4.0, and most desirably from 3.3 to 4.0. Other aspects, objects and advantages of the present invention will be apparent from the following disclosures of Figures 1 and 2. The claimed apparatus and process provide various advantages over the state of the art, including: (1) enabling continuous processing of the content of a slurry reactor from the point of discharge of the polymerization slurry effluent through a discharge valve; a first flash tank; a seal chamber; a seal chamber outlet reducer; and from there to a second flash tank, (2) significantly increase the ethylene concentration in the liquid medium of the closed-loop reactor, thereby increasing the reactor performance, (3) significantly increase the weight percentage (% by weight) of polymer solids in the polymerization slurry circulating in the polymerization zone in the closed loop reactor. From Desirably, the weight percent polymeric solids in the polymerization slurry is greater than 45, more desirably from 45 to 65, still more desirably from 50 to 65, and most desirably from 55 to 65%. Another objective of the present invention is to increase the space time (STY) performance, expressed in • terms of pounds per hour-gallon (lbs / hr-gal). Desirably, the STY is greater than 2.6, more desirably from 2.6 to 4.0, and most desirably from 3.3 to 4.0. Other aspects, objectives and advantages of the present invention will be apparent from the following disclosures of Figures 1 and 2. The claimed apparatus and process provide various advantages over the state of the art, including: (1) enabling processing continuous of the content of a slurry reactor from the point of discharge of the polymerization slurry effluent through a discharge valve; a first flash tank; a seal chamber; a seal chamber outlet reducer; and thence to a second flash tank, (2) significantly increase the ethylene concentration in the liquid medium of the closed-loop reactor, thereby increasing the reactor efficiency, (3) significantly increasing with dissolved monomer, co-monomer, molecular weight control agents, such as hydrogen, anti-static agents, anti-clogging agents, depo-bers, and other process additives.

As used herein, the term "space time yield" (STY) means the rate of polymer production per unit volume of closed-loop reactor or volume of polymerization slurry. As used herein, the term "catalyst productivity" means the weight of the polymer produced by weight • of catalyst introduced in the closed loop reactor. As used herein, the term "residence time of the polymer" means the average duration that a polymer particle remains within the closed loop reactor. The present invention is applicable to any mixture comprising a slurry of polymeric solids and a liquid medium comprising an inert diluent and unreacted polymerizable monomers, including slurries resulting from the polymerization of olefins. The olefin monomers generally employed in such reactions include 1-olefins having from 2 to 8 carbon atoms per molecule. Typical examples include ethylene, propylene, butene, pentene, hexene and octene. Other examples include vinyl aromatic monomers, such as styrene and substituted alkyl styrene, geminally distributed monomers, such as isobutylene and cyclic olefins, such as norbornene and vinyl norbornene. Typical diluents employed in such olefin polymerizations include aliphatic hydrocarbons having 3 to 8, preferably 3 to 4, carbon atoms per molecule, such as propane, isobutane, propylene, n-butane, n-pentane, isopentane, n-hexane, isooctane, and the like. Of these diluents, those of 3 to 4 carbon atoms per molecule are preferred, and isobutane is most preferred. The discharge rate of the polymerization effluent is such as to allow a continuous process stream of the slurry closed-loop reactor from the point of discharge of the liquefied polymerization effluent through a single-point discharge valve and also to through the first flash tank and the associated vapor recovery and solids recovery systems. The discharge rate of the polymerization effluent is such as to maintain a constant pressure in the slurry reactor and eliminate intermittent high pressure pulses associated with a discharge of a portion of the reactor contents that occurs with the settling legs in the grout reactors. The temperature at which the polymerization effluent that is discharged from the reactor is heated, during transit to the first flash tank for vaporization, is below the melting temperature of the polymer. This can be achieved by proper heating of this first transfer conduit. The amount of heat to be delivered to the polymerization effluent during its transit through this first conduit to the first flash tank should preferably be at least equal to the amount of heat that equals the heat of • vaporization of that amount of inert diluent that will vaporize by flash in the first flash tank. This will then provide that the concentrated polymer solids formed in the first flash tank are passed to the second flash tank to pass thereto at a higher solids temperature and thus facilitate the removal of residual diluent in the pores of such polymer solids by the operation of the second flash tank. That amount of heat transferred to the polymerization effluent during its transit through the first transfer conduit to the first flash tank may be even greater, provided only that the amount of heat thus transferred does not cause the polymer solids therein to be transferred. heat at a temperature such that they tend to melt or agglomerate with each other. The concentrated polymeric / slurry solids are discharged from the first flash tank to an outlet seal chamber of the first flash tank of a length (1) and a diameter (d) such as to provide sufficient volume to maintain a volume of Concentrated polymer / slurry solids to maintain a pressure seal in the outlet seal chamber. The concentrated polymeric / slurry solids are discharged from the outlet seal chamber through an outlet seal chamber reducer to a second transfer conduit that communicates the concentrated polymer / slurry solids as a plug flow to a second tank. flash. The output seal chamber reducer is defined by substantially straight sides inclined at an angle with the horizontal greater than or equal to the slip angle of the concentrated polymeric / slurry solids. The pressure for the first flash step will vary depending on the nature of the diluent and the unreacted monomers and the temperature of the polymerization effluent. Typically, pressures in the range of about 140 to about 315 psi absolute can be employed; more preferably, from about 200 to about 270 psi absolute; and most preferably from about 225 to about 250 psi absolute. The heat exchange fluid used to condense the vapor of the first flash passage is at a temperature in the range of about 65 to about 150 ° F. A preferred embodiment uses a heat exchange fluid at a temperature of about 75 to about 140"F. A more preferred embodiment uses a heat exchange fluid at a temperature of about 85 to about 130. "F. A further understanding of the present invention will be provided by reference to Figure 1, which illustrates a system comprising an embodiment of the invention. In the embodiment illustrated in Figure 1, the polymerization is carried out in a closed-loop reactor 1. It will be understood that although the closed-loop reactor 1 is illustrated with four vertical legs, the closed-loop reactor 1 may be equipped with more legs, desirably eight or more legs, more desirably between 8 and 20 legs, in the most desirable manner between 8 and 16 legs, and in the most desirable manner with 12 legs. The polymerization slurry is circulated directionally through the entire closed loop reactor 1, as illustrated by arrows A-D by means of one or more pumps, such as axial flow pumps 2A and 2B. Desirably, the closed loop reactor 1 is equipped with multiple pumps, where each pump is dedicated to an even number of legs, such as for example four legs, six legs, eight legs, etc. Diluent, co-monomer and monomer are introduced into the closed-loop reactor 1 from the diluent storage container 40, the co-monomer storage container 41, and the monomer source 42, through their respective treatment beds., 38 and 29 through conduits 5, 4 and 3, respectively, connected to conduit 6. The catalyst is added to the closed loop reactor 1 through one or more catalyst feed systems 7A and 7B. Normally, the catalyst is introduced into a hydrocarbon diluent. The polymerization slurry can be removed from the closed-loop reactor by continuous discharge through a discharge conduit 8A. It will be understood that the closed-loop reactor 1 may be equipped with one or more discharge conduits 8A. It will also be understood that the discharge conduit (s) 8A can be operated in a continuous or batch mode, but desirably a continuous mode. The discharge conduit 8A extends a distance through a portion of the wall of the closed loop reactor 1 and towards the circulating polymerization slurry. By extending a distance to the polymerization slurry, the discharge conduit 8A can remove polymerization effluent from the circulating polymerization slurry over a defined area from near or adjacent to the inner wall of the closed loop reactor 1 at a distance extending to the circulating polymerization slurry. In this way, a greater percentage by weight of polymeric solids can be formed within conduit 8A and eventually removed from the closed loop reactor 1 than the percentage by weight of polymer solids within the otherwise circulating polymerization slurry. A pressure control system (not shown in Figure 1) operates in concert with the discharge conduit 8A. The discharge conduit 8A and the pressure control system 410 are illustrated more clearly in Figures 3 and 4 and will be discussed in more detail below. The polymerization effluent passes from the discharge conduit 8A to the discharge valve 8B to a conduit 9 which is provided with a line heater 10 and to the first flashing tank 11 which separates vaporized liquid medium from the polymeric / slurry solids. The conduit 9 has indirect heat exchange means such as a flash line heater • 10. The vaporized liquid medium comprising diluent and unreacted monomers leaves the first flash tank 11 via the transfer conduit 12, through which it passed to a separator, such as a cyclone separator, illustrated by reference numeral 13 , which separates trapped polymer solids M • of steam. The polymer solids separated by the cyclone separator 13 are passed via line 14 through a set of double valves 14A designed to maintain a pressure seal, below the cyclone separator 13 to a second flash tank 15 at a lower pressure. The double valve assembly 14A includes the valves 14B and 14C. The valve assembly 14A, in conjunction with the conduit 14, operates to periodically discharge polymer solids that have been collected in the conduit 14 from the cyclone separator 13. The valve assembly 14A also maintains the pressure differential between the pressurized environment upper in the cyclonic separator 13 and the lower pressure environment in the second flash tank 15. In the operation of the valve assembly 14A, the valves 14B and 14C are opened and closed sequentially. At the beginning of this sequence, the valve 14B is opened and the valve 14C is closed allowing the polymeric solids of the cyclone separator 13 to accumulate in the conduit 14. Over time and / or when sufficient polymeric solids are collected in the conduit 14 , the • valve 14B closes, capturing a portion of the upper pressure environment of cyclone separator 13 in conduit 14. After valve 14B closes, valve 14C opens and polymer solids accumulated in conduit 14 are forcedly discharged to the flash tank 15 by the pressure differential between the upper pressure environment in line 14 and the lowest pressure environment in the flash tank 15. After discharge of the polymer solids from line 14 to flash tank 15, valve 14C close Once the valve 14C closes, the valve 14B is opened, upon which occur the polymer solids will again accumulate in the conduit 14 from the cyclonic separator 13. The above sequence is then repeated. Referring back to the first flash tank 11, the polymeric / slurry solids concentrated at the bottom of the first flash tank 11 are continuously seated by sliding along the straight line bottom surface 16 thereof to the seal chamber 17, which is illustrated in an amplification in Figure 2. A level 43 of polymeric solids / slurry is maintained in the seal chamber 17 to eliminate plugging tendencies in the first flash tank 11 and to form a pressure seal of so that the first flash tank 11 can operate at a substantially higher pressure than the second flash tank 15. The polymeric / slurry solids are continuously discharged from the seal chamber 17 to the second flash tank 15 at a lower pressure. The length (1), the diameter (d) and the volume of the seal chamber 17 and the geometry of the seal chamber outlet reducer 18 are selected so as to provide a variable residence time and provide a continuous packing flow. of polymeric solids / slurry concentrates to minimize "dead" space and reduce tamponade tendencies. The length of the seal chamber 17 should be sufficient to allow measurement and control of particle level (polymer solids). The measurement and control of particle level can be achieved by means of a nuclear level indicator system 18D. The nuclear level indicator system 18D includes a nuclear radiation source (not shown) and a level 18A receiver or element in signal communication with a level indicator controller 18B. In operation, the level element 18A generates a signal proportional to the level of particles in the seal chamber 17. This signal is transmitted to the level indicator controller 18B. In response to this signal and a pre-set value, the level indicator controller 18B sends a signal through a conduit (illustrated by broken line 18C) to a control valve 18E that selectively controls the discharge of polymeric solids into a conduit 19. Typical residence times for the polymeric / slurry solids concentrated in the seal chamber 17 are from • 5 seconds to 10 minutes, preferably 10 seconds to 2 minutes, and most preferably 15 to 45 seconds. The continuous flow of plugging of polymeric solids / slurry concentrates forms a pressure seal where the concentrated polymer / slurry solids have a 1 / d ratio within the seal chamber 17 which is typically 1.5 to 8, of • preference is from 2 to 6, and most preferably from 2.2 to 3. Typically, the sides of the output reducer of the seal chamber 18 are inclined, relative to the horizontal, 60 to 85 *, preferably 65 to 80", and most preferably 68-75 'The geometry of the output reducer of the seal chamber 18 is defined by substantially straight sides inclined at an angle with the horizontal greater than or equal to the slip angle of the solids. polymer / slurry concentrates and communicates the concentrated polymeric / slurry solids to a second transfer conduit 19 which communicates with a feed inlet 0 of the flash tank 15. In the flash tank 15, substantially all the inert diluent and unreacted monomer remnants in the concentrated polymerization effluent is vaporized and carried to the head via conduit 20 to a second cyclonic separator 21. 5 Referring now to cyclone separator 13, the portion The largest of the liquid medium in the polymerization effluent can be brought to the cyclone separator 13 as steam. The vapor, after a portion of the catalyst and trapped polymer solids is removed therefrom, is passed via conduit 22 through a heat exchange system 23A, where the steam at an absolute pressure of about 140 to about of 315 psi is condensed by indirect heat exchange with a heat exchange fluid such as to eliminate the need for compression. The portion of the catalyst and polymeric solids not removed from the cyclonic separator 13 is generally smaller in size and can be referred to as "fine particles", "fine polymer particles" and / or "fine particles of catalyst". These fine particles generally include unreacted and / or sub-reacted catalyst. The heat exchanger system 23A includes a heat exchanger 23E and a circulating warm water pump 23B connected to the heat exchanger 23E via the conduit 23C. A tempered water temperature control valve 23D is connected to the heat exchanger 23E and the circulating water pump 23B via conduits 23F and 23G, respectively. The cooling water from a cooling water source (not shown) is conveyed via a cooling water conduit 23H to the conduit 23G between the control valve 23D and the circulating pump 23B. A temperature indicating controller (TIC) 23J is connected between the control valve 23D and the conduit 23C. A temperature element 23K resides between the controller 23J and the conduit 23C. The heat exchanger system 23A operates for • control the amount of steam condensed in the heat exchanger 23E. This is achieved by controlling the flow of cooling water introduced into the conduit 23G from the conduit 23H by discharging the heated water formed in the heat exchanger 23E. The heated water from the heat exchanger 23E is conveyed to the control valve 23D via the conduit 23F. He • heated water leaves control valve 23D via conduit 231. More specifically, cooling water from conduit 23H entering conduit 23G is mixed with warm water circulating in conduit 23G, its mixture entering the pump 23B. The water leaving the pump 23B enters the conduit 23C, a portion of which makes contact with the temperature element 23K, en route to the heat exchanger 23E. The temperature element 23K generates a signal proportional to the temperature in the conduit 23C. The signal is transported to the controller or temperature indicator 23J. In response to this signal and a pre-set temperature value, the temperature indicating controller 23J sends a signal through a signal conduit (illustrated by broken line 23L) to the control valve 23D, which selectively controls the volume of heated water leaving the heat exchanger system 24A through of the conduit 231. The condensed liquid medium formed in the heat exchanger 23E includes diluent, unreacted / su-reacted catalyst, polymer solids and unreacted monomers. This condensed liquid medium is then passed to an accumulator 24B via a conduit 22A. A pump 25 is provided for transporting the condensed liquid medium from the accumulator 24B back to the polymerization zone by means of a conduit 26. In this way, the unreacted / sub-reacted catalyst and the polymer solids not removed by the cyclone separator 13 are returned for further polymerization to the closed loop reactor 1. The polymer solids in the second flash tank 15 at lower pressure are passed via a conduit 27 to a conventional dryer 28. The steam leaving the secondary cyclonic separator 21, after filtering in a filter unit 29, is passed through a duct 30 to a compressor 31 and the compressed vapors are passed through a duct 32 to a condenser 33 where the vapor is condensed and the condensate is passed through the conduit 34 to a storage vessel 35. The liquid medium condensed in the storage vessel 35 is typically ventilated in the head for removal of light-end contaminants. . The inert diluent can be returned to the process by a treating bed 37 to remove catalyst or distillate poisons in unit 36 for more complete removal of the light ends and then returned to the process through a treatment bed. Turning now to Figure 3, a portion of a wall 310 of the closed loop reactor 1 through which the discharge conduit 8A extends is illustrated. The discharge conduit 8A can be extended to the reactor at various angles. Desirably, the discharge conduit 8A extends towards the closed-loop reactor substantially at a right angle relative to the wall 310. The wall 310 includes an internal surface 312 and an external surface 314. The internal surface 312 holds the slurry. of circulating polymerization illustrated by the directional arrows 318. The discharge conduit 8A has an upper portion 316A, and a continuous side 316B. Portions of side 316B define an opening 320. Opening 320 has vertical opening dimensions vi and v2 defined by walls 320A and 320B of side 316B. Desirably, dimension vi is greater than dimension v2. The opening 320 has horizontal opening dimensions hl and h.2 (not shown). The opening 320 may be formed in any suitable shape, such as rectangular, oval or a combination thereof. In one embodiment, the opening 320 may be conical or bucket-shaped. The opening 320 communicates with a channel 322 defined by the internal surfaces of the upper part 316A and the side 316B. The channel 322 carries the captured polymerization slurry, illustrated by the directional arrow 324 to the discharge valve 8B (not shown). • The opening 320 is dimensioned and positioned relative to the direction of movement of the circulating polymerization slurry 318. Desirably, the aperture 320 is in a position substantially frontal to the direction of the circulating polymerization slurry 318. More Desirable, the opening 320 faces the direction of the circulating slurry 318. In this manner, a portion of the polymerization slurry 324 containing polymer solids is removed from the circulating polymerization slurry 318 over an area from near or adjacent to the inner wall. 312 of the closed-loop reactor 1 at a distance extending to the circulating polymerization slurry 318. In this way, a higher weight percentage of polymer solids can be formed within the conduit 8A than the percentage by weight of polymer solids within the circulating polymerization slurry in another way. This increase in the weight percentage of polymeric solids may depend on the location of the discharge conduit 8A along the closed-loop reactor 1, the insertion depth of the discharge conduit 8A into the closed-loop reactor, the size and the configuration of the opening 320, the orientation of the opening 320 relative to the direction of the circulating polymerization slurry, and the weight percentage of polymer solids in the circulating polymerization slurry 318. For example, a calculated increment of 1 is observed. at 5% by weight with a discharge conduit 8A having a dimension vi of approximately 5 inches and a dimension hl of approximately 1 inch. The discharge conduit 8A was placed 10 feet downstream of a 90 'bend in the closed loop reactor 1 in a portion of the wall 314 of the closed loop reactor adjacent to the ground. The discharge conduit 8A extends approximately 5.5 inches into the circulating polymerization slurry stream. The speed of the circulating polymerization slurry was in the range of 28 to 34 feet / second with a weight percentage of polymer solids in the range of 48 to 53. Turning now to Figure 4, the pressure control system 410 is illustrated. The pressure control system 410 operates to maintain a substantially uniform pressure within the closed loop reactor 1 by controlling the discharge of polymerization effluent from the closed loop reactor 1 via the discharge conduit 8A. The control system 410 also operates to prevent plugging of the discharge conduit 8A by the polymer solids during pressure fluctuations within the closed loop reactor 1 and / or when the flow of polymerization effluent from the discharge conduit 8A to the conduit 9 is interrupted. and / or arrested. The pressure control system 410 includes a first source of inert diluent 412, such as isobutane, and an inert diluent conduit 414 in communication with a conduit 416 of the closed loop reactor. The flow of inert diluent through the inert diluent conduit 414 to the conduit 416 of the closed-loop reactor is controlled by means of the control valve 418 in concert with a flow member 420 and a flow indicator controller 422. The purpose of dosing the flow of inert diluent of the first source of inert diluent 412 to the closed loop reactor 1 is to prevent plugging of the conduit 416 by the polymer solids. In this manner, a closed-loop reactor pressure element 441 (discussed below), in communication with the closed-loop reactor duct 416, can more accurately monitor the pressure in the closed-loop reactor 1. The system pressure control 410 further includes a second source of inert diluent 424 and a third source of inert diluent 426. Inert diluent, such as isobutane, from the second source of inert diluent 424 flows to a conduit 428 to a control valve 430 which is in fluid communication with a conduit 432. The control valve 430, in concert with a flow member 431 and a flow indicator controller 433, meters the flow of inert diluent from the second source of inert diluent 424 into the conduit 432. The conduit 432 is in fluid communication with a conduit 434 and the discharge conduit 8A, terminating in the discharge conduit 8A at a point between the reactor circuit cer 1 and discharge valve 8B. The purpose of dosing the flow of inert diluent of the second source of inert diluent 422 to conduit 432 is to prevent plugging of conduit 432 by polymer solids, which could otherwise flow back into conduit 432 from discharge conduit 8A . Additionally, the flow of inert diluent of the second source of inert diluent 422 also prevents plugging of conduit 434 and control valve 440 by polymer solids that could flow back to conduit 432 of discharge conduit 8A. Inert diluent of the third source of inert diluent 426 flows to a conduit 438 to a control valve 440 that is in fluid communication with the conduit 434. As will be explained in more detail below, in the case of a sufficient pressure fluctuation inside the closed-loop reactor 1, the control valve 440 operates to initiate a sufficient flow under sufficient pressure of inert diluent from the third source of inert diluent 426 to purge and / or discharge polymeric solids from the discharge conduit 8A to the circuit reactor closed 1. In this case, generally the flow of inert diluent from the third source of inert diluent 426 to conduit 432 will be greater than the flow of inert diluent of the second source of inert diluent 424 to conduit 432. For example, the flow of Inert diluent of the second inert diluent source 424 to the discharge conduit 8A may be in a range of 0.5 to less than 2.0 gallons / minute. The flow of inert diluent from the third inert diluent source 426 to the discharge conduit 8A may be in the range of 2.0 to 20 gallons / minute. The pressure element 441 of the closed loop reactor and a pressure indicating controller 442 carry out various functions. As previously mentioned, the pressure element 441 monitors the pressure of the closed-loop reactor 1 via the conduit 416. In response to this pressure, the pressure element 441 of the closed-loop reactor generates a signal proportional to the pressure in the conduit 416. This signal is conveyed to the pressure indicating controller 442. In response to this signal and a pre-set pressure value, the pressure indicating controller 442 sends a signal through a signal conduit (illustrated by the broken line 444) to the valve discharge valve 8B and control valve 440. During normal operations of the closed-loop reactor, the discharge valve 8B is positioned to allow the flow of polymerization effluent from the discharge conduit 8A to the conduit 9. At the same time, the control 440 is closed, preventing the flow of inert diluent from the third source of inert diluent 426 to the discharge conduit. When sufficient pressure fluctuations occur and / or when partial depressurization is detected in the closed loop reactor 1 by the pressure element 441 of the closed loop reactor, the signal generated by the pressure indicating controller 442 causes the discharge valve 8B Close and control valve 440 open. By closing the discharge valve 8B, in this way interrupting the discharge of the closed-loop reactor 1, the pressure inside the closed-loop reactor 1 can be restored. By opening the control valve 440 and flowing sufficient volumes of inert diluent from the third source of inert diluent 426 to the discharge conduit 8A under sufficient pressure, the polymer solids remaining in the discharge conduit 8A between the discharge valve 8B and the closed-loop reactor 1 may be expelled and / or purged from the discharge conduit 8A and into the closed-loop reactor 1. Additionally, maintaining a sufficient flow of inert diluent, continuous or otherwise, to and / or through the conduit of discharge 8A while the discharge valve 8B is closed, the polymer solids within the closed loop reactor 1 are prevented from entering and / or substantially accumulating in the discharge conduit 8A and / or plugging the discharge conduit 8A. Upon returning from normal operations, the control valve 440 closes, terminating the flow of inert diluent from the third source of inert diluent 426 and the discharge valve 8B opens to resume the flow of polymerization effluent through the discharge conduit 8A to the conduit 9.

Having broadly described the present invention, it is believed that it will be even more apparent by reference to the following examples. It will be appreciated that the examples are presented¬ • two only for purposes of illustration and should not be construed as limiting the invention. E xamples Example 1 A typical polymerization process can be conducted at a temperature of about 215"F and absolute pressure • 565 psi. An example of such a process would result in a polymerization effluent of about 83,000 pounds per hour, comprising about 45,000 pounds per hour of polyethylene polymer solids and about 38,000 pounds per hour of isobutane and unreacted monomers. The continuously discharged polymerization effluent is flashed in the first flash tank at an absolute pressure of about 240 psi and a temperature of about 180 ° F to remove about 35,000 pounds per hour of diluent and solvent vapors at the head. unreacted monomer and particulate or entrapped materials. Auxiliary heat to impart an additional amount of heat to the polymerization effluent is supplied by appropriate heating means during transit between the discharge valve and the first flash tank. After removal of the fine particles, the isobutane vapor is condensed, without compression, by heat exchange at an absolute pressure of about 240 psi and a temperature of about 135"F. Polymer / slurry solids that are discharged from the bottom of the first flash tank to the seal chamber they form a continuous flow of plugging of polymeric solids / slurry concentrates, which provides a pressure seal, with a 1 / d ratio of the polymer solids plug / slurry of 2.5 in one seal chamber of 8 feet 4 inches long having a 1 / d ratio of 5.5 and with a cone angle of around 68 'in the seal chamber outlet reducer.The residence time of the continuous flow of plugging The concentrated polymeric / slurry solids is about 16 seconds.The concentrated polymeric / slurry solids are discharged continuously from the bottom of the first flash tank at a temperature of about 180 ° F and an absolute pressure of about 240 psi through a seal chamber, seal chamber outlet reducer, and a second transfer conduit to a feed inlet in a second flash tank. The liquid medium remaining in the concentrated polymeric / slurry solids communicated to the second flash tank is flashed at a temperature of about 175 * F and an absolute pressure of about 25 psi to remove about 4,300 pounds per hour of isobutane and monomers without react that are condensed by compression and heat exchange. Example 2 A typical ethylene polymerization process can be further conducted at a temperature of about 215 ° F and an absolute pressure of 565 psi An example of such a process would result in a polymerization effluent from around • of 83,000 pounds per hour, comprising about 45,000 pounds per hour of polyethylene polymer solids and about 38,000 pounds per hour of isobutane and unreacted monomers. The continuously discharged polymerization effluent is flashed in the first flash tank at an absolute pressure of about 240 psi and a temperature of about 175 ° F. • to remove approximately 23,000 pounds per hour of diluent and unreacted monomer vapors and trapped particulate from the head. After removal of the fine particles, the isobutane vapor is condensed, without compression, by heat exchange at an absolute pressure of about 240 psi and at a temperature of about 112"F. The polymeric / slurry solids that are discharged from the bottom of the first flash tank to the seal chamber form a continuous flow of plugging of polymeric solids / slurry concentrates, which provides a pressure seal, with a 1 / d ratio of 0 polymer solids / slurry plug of 2.5 in a seal chamber of 8 feet 4 inches long with a 1 / d ratio of 5.5 and with a cone angle about 68 'in the output reducer of the seal chamber. The residence time of the continuous flow of plugging of polymeric solids / slurry concentrated in the seal chamber is about 16 seconds. About 60,000 pounds per hour of polymeric solids / slurry concentrates are continuously discharged from the bottom of the first flash tank at a temperature of about 175 * F and an absolute pressure of about 240 psi through a seal chamber, reducer of output of seal chamber and a second transfer conduit to a feed inlet in a second flash tank. The liquid medium remaining in the concentrated polymeric / slurry solids communicated to the second flash tank is flashed at a temperature of about 125 ° F and at an absolute pressure of about 25 psi to remove about 16,000 pounds per hour of isobutane and monomer without react, which are condensed by compression and heat exchange Example 3 An example of a typical ethylene polymerization process was carried out in an eight-leg, 20-inch reactor, with settling legs having an overall length of about 833 feet and a volume of 11,500 gallons The reactor was equipped with a single flash tank (requiring 100% compression of all the diluent discharged from the reactor), a single circulating pump of 460-480 kilo-watts having a pump head in the range of 85 to 110 feet, producing a circulation rate in the range of 21,000 to 28,000 gallons per minute (gpm) and operated in a discontinuous discharge mode a) The temperature and polymerization pressure in the reactor would be between 215 and 218 'F and 565 psi absolute. In the process of Example 3, the density of the reactor slurry is in the range of 0.555 to 0.565 g / cc, a range of polymer production rate of 28,000 to 31,000 pounds per hour, maintaining a percentage by weight of concentration of solids in the reactor in the range of 46 to 48% with a residence time of polymer in the range of 0.83 to 0.92 hours. The space time performance (STY) was in the range of 2.4 to 2.7. The data and results of Example 3 are further illustrated in Table 1. Example 4 Another example of a typical ethylene polymerization process illustrating high loading of polymer solids was carried out in an eight leg, 20 inch reactor, having an overall length of 833 feet and a volume of 11,500 gallons. The reactor of Example 4 was equipped with double flash tanks, a single discharge chute, two circulating pumps in series consuming a total of between 890 and 920 kilo-watts, producing a total head of pumping in the range of 190 to 240 feet , producing a circulation rate in the range of 23,000 to 30,000 gpm and operated in a continuous discharge mode. The temperature and polymerization pressure in the reactor would be between about 217 and 218 'F and 565 psi absolute. In the process of Example 4, a polymerization effluent having a reactor slurry density in the range of 0.588 to 0.592 g / cc, a polymer production rate in the range of 38,000 to 42,000 pounds per hour was produced, maintaining a percentage by weight of solids concentration in the reactor in • the range of 54 to 57% with a residence time of polymer in the range of 0.68 to 0.79 hours. The space time (STY) performance was in the range of 3.3 to 3.7. The data and results of Example 4 are further illustrated in Table 1. The continuously discharged polymerization effluent is flashed in the first flash tank at an absolute pressure of about 240 psi and a temperature of about 175 ° F to remove at the head around 16,000 pounds per hour of diluent and unreacted monomer vapors and trapped particulate materials. After removal of the fine particles, the isobutane vapor is condensed, without compression, by heat exchange at an absolute pressure of about 240 psi and a temperature of about 112 'F. The polymeric / slurry solids that are discharged from the bottom of the first flash tank into the seal chamber form a continuous flow of plugging of polymeric solids / slurry concentrates that provides a pressure seal, with a 1 / d ratio of the polymeric solids plug / 2.5-inch grout and a seal chamber 8 feet 4 inches long, with a 1 / d ratio of 5.5 and with a cone angle of around 68 'in the seal chamber outlet reducer. The residence time of the continuous flow of plugging of polymeric solids / slurry concentrated in the seal chamber is about 16 seconds. The concentrated polymer / slurry solids are continuously discharged from the bottom of the first flash tank at a temperature of about 175"F and an absolute pressure of about 240 psi through a seal chamber, seal chamber outlet reducer and a second transfer duct to a feed inlet in a second flash tank.The liquid medium remaining in the concentrated polymeric / slurry solids communicated to the second flash tank is flashed at a temperature of about 125 ° F and at an absolute pressure about 25 psi to remove about 16,000 pounds per hour of unreacted isobutane and monomer, which are condensed by compression and heat exchange.

Table 1 Discussion In view of the above description and the examples, various observations can be made regarding the apparatus and the process.

It has been found that by increasing the head and flow capacity of the circulation pump (s) of the closed-loop reactor, a higher percentage by weight of solids in the reactor can be circulated. It has also been found that reaching the required head and flow from a pump is increasingly difficult as the percentage by weight of solids increases above 45% by weight and / or as the length of the reactor increases. Therefore, the use of two pumps in series allows to double the head capacity of pumping and a resulting increase in the percentage of solids. The increased weight percentage of solids in the closed loop reactor increases the residence time of the catalyst, which for chromium oxide and Ziegler-Natta catalysts, increases the catalyst productivity. It is possible to choose to take advantage of the higher percentage of solids and the longer residence time by maintaining the constant production rate or rate at a reduced catalyst feed rate and improving catalyst performance. Another alternative is to keep the catalyst feed rate constant and increase reactor performance and, therefore, increase the STY at almost constant catalyst productivity. The higher solids also increase the weight percentage of solids removed from the reactor, which reduces the cost of isobutane processing in the recycling equipment. Desirably, the higher solids are removed continuously. Continuous discharge can occur through a single point discharge line. In a closed-loop reactor, it is not always possible to place the continuous discharge line in an optimum place to take advantage of the centrifugal force to increase the percentage by weight of solids and therefore reduce the amount of isobutane trapped with the polymeric solids. It has been observed that a specifically designed tube, as illustrated in Figure 3, inserted into the closed-loop reactor can increase the weight percentage of solids removed from the reactor. This tube insert will work in any section of the closed-loop reactor and in a straight section, which will increase the percentage by weight of solids to a value equal to that in a place that harnesses the centrifugal force to concentrate solids. With the development of circulation capacity of high percentage by weight of solids in the closed-loop reactor and the two-stage flash, the need to concentrate solids in the discharge of the reactor is reduced compared to conventional closed-loop reactor operations having low solids circulation, flash in a single stage, continuous discharge line, and continuous discharge or otherwise. Therefore, the conventional settlement legs of the closed loop reactor, which are designed to maximize the concentration of polymer solids before discharge, can be replaced with a continuous discharge line, which simplifies the system mechanically, reduces the costs of capital, improves safety, reduces maintenance and improves reactor control. Settling legs require routine maintenance due to their tendency to plug and can form material that clogs downstream polymer handling equipment. The maximum concentration of ethylene in the closed loop reactor is limited by the settling legs due to the tendency of the polymer to develop in the legs at high concentrations of ethylene between discharges, and therefore plug the leg. The continuous discharge eliminates this tendency. Another advantage of continuous discharge is a better response to a sudden drop in reactor pressure, which can occur if the ethylene flow is rapidly reduced. Under this condition, the settling legs will stop the discharge and can be plugged with polymer in minutes. One development that can increase the efficiency of the flash system in two stages is the continuous flash line heater. The heater would vaporize up to 100% of the diluent discharged from the reactor with the polymer, which would allow a greater recovery of the diluent by the intermediate pressure condenser. Diluent recovery through the first flash tank would reduce energy and capital costs. Conventional single-stage low pressure diluent recovery systems include compression, distillation and treatment, which have high capital and operating costs. The flash line heater would increase the temperature of the polymer in the downstream dryer system and create the potential for lower levels of volatiles in the final product, which would reduce variable costs, improve safety and help meet environmental standards. The first flashing tank provides a flashing step at intermediate pressure that allows simple condensation of the diluent and return to the reactor. The flash line heater would be able to supply enough heat to vaporize up to 100% of the diluent in the first flash tank. Diluent vapors and fine particles of unreacted / sub-reacted catalyst and polymer would go to the head from the flash tank to the cyclone separator. The bulk of the polymer exits through the bottom of the first flash tank through the seal chamber to the second flash tank. Attached to the bottom of the first flash tank is the seal chamber which provides a low residence time plugging flow area to control the polymer level and maintain the pressure in the first flash tank. The seal chamber is designed to accommodate a range of polymer forms from concentrated slurry to dry polymer.

The head current of the first flash tank is received by the cyclone separator, which removes most of the fine polymer particles and returns them to the bulk of the polymer flow in the second flash tank through a two-valve system that it allows the fine particles to accumulate between the valves, then they are discharged through the bottom valve while maintaining the pressure in the first flash system. The head stream of the cyclone separator contains some unreacted / sub-reacted catalyst and fine polymer particles. These particles are carried with the diluting vapor to the condenser, trapped with the liquid diluent after the condensation, collected in the accumulator and returned to the reactor in the diluent. The condensation and storage systems are designed and operated to adapt to fine particles. The condenser provides liquefaction at low capital costs and diluent variables removed from the reactor with the polymer via the first flash tank. Conventional single-flash tank systems flash the polymerization effluent at just above ambient pressure, which requires compression to liquefy the diluent before it is recycled to the closed loop reactor. An intermediate pressure flash provides condensation with a commonly available cooling medium, such as plant cooling water. The condenser system is immersed in diluent and is designed to accommodate a level of fine particles without accumulation or plugging. The condenser is cooled by a warm water system that controls the condensing temperature to reach the appropriate vapor pressure in the accumulator to allow efficient control of the pressure by means of the pressure control valve in the accumulator vent. The tempered water system of the condenser is a closed circuit for pumping cooling water, whose temperature is controlled by dosing fresh cooling water as needed. The accumulator receives the condensed diluent and the fine particles of catalyst / polymer and pumps the mixture back to the closed loop reactor based on the level control in the accumulator. The accumulator has a bottom shape designed to accommodate fine particles. A vent in the accumulator purges the accumulated thinner / non-condensable diluent and controls the pressure in the first flash system. The second flash tank, which operates at pressure just above the ambient, receives polymer from the seal chamber of the first flash tank. Full vaporization, if not already achieved in the first flash tank, will occur in the second flash tank. The polymer leaves the bottom of the second flash tank to the drying system. The flash line heater would increase the temperature of the polymer, allowing the dryer system to remove residual volatiles more efficiently and effectively. The head of the second flash tank will be diluent vapor not recovered in the first flash system and will be filtered and compressed for return to the closed loop reactor. Although the present invention has been described and illustrated by reference to particular embodiments, those skilled in the art will appreciate that the invention lends itself to many different variations not illustrated herein. Then, for these reasons, reference should be made only to the appended claims in order to determine the true scope of the present invention. Although the appended claims have simple dependencies in accordance with the practice of patents in the United States, each of the features of any of the dependent claims may be combined with each of the features of other dependent claims or the main claim.

Claims (27)

1. CLAIMS 1. An apparatus for capturing a greater percentage by weight of polymer solids from a circulating slurry in a closed-loop reactor, than the weight percentage of solids in the circulating slurry, the circulating slurry being circulated in a direction in the Closed loop reactor, comprising: a duct having a first end, wherein said first end extends a distance to the closed loop reactor, said duct having portions defining an opening, wherein said opening is positioned relative to the direction of the circulating grout.
2. 2. The apparatus of claim 1, wherein the opening is facing in the direction of the circulating slurry.
3. 3. The apparatus of claim 1, wherein a portion of the conduit extends outwardly from the closed-loop reactor.
4. The apparatus of claim 3, wherein the polymer solids are discharged from the closed-loop reactor through the portion of the conduit extending outward from the closed loop reactor.
5. The apparatus of claim 4, wherein the polymer solids are continuously discharged from the closed-loop reactor through the portion of the conduit extending outward from the closed loop reactor.
6. 6. A process for capturing a higher weight percent polymeric solids from a circulating slurry in a closed loop reactor than the weight percent polymer solids in the circulating slurry, the circulating slurry being circulated in a direction in the circuit reactor Closed, comprising the step of: extending a distance to the closed-loop reactor a conduit having portions defining an opening, wherein said opening extends towards the circulating slurry.
7. The process of claim 6, including the step of placing the opening in a direction substantially facing the direction of flow of the circulating slurry.
8. The process of claim 6, including the step of extending a portion of the conduit out of the closed loop reactor.
9. The process of claim 8, including the step of discharging the polymer solids from the closed-loop reactor through the portion of the conduit extending outward from the closed-loop reactor.
10. The process of claim 9, including the step of continuously discharging polymer solids from the closed loop reactor through the portion of the conduit extending outward from the closed loop reactor.
11. 11. An apparatus for purging polymeric solids from a conduit connected to a closed-loop reactor and in fluid communication with the closed-loop reactor, comprising: a sensor; a first valve in fluid communication with the conduit; a second valve positioned between a first inert diluent and the conduit, wherein the first inert diluent is in fluid communication with the conduit between the closed-loop reactor and the first valve; where, in response to a signal produced by the sensor, the first valve is closed and the second valve is opened allowing the first inert diluent to enter the conduit in sufficient quantities and under sufficient pressure to purge polymeric solids from the conduit.
12. 12. The apparatus of claim 11, wherein the sensor is a pressure sensor.
13. The apparatus of claim 11, wherein the conduit has a first end, wherein said first end extends a distance to the closed loop reactor, where portions adjacent the first end define an opening.
14. The apparatus of claim 11, further comprising: a third valve positioned between a second inert diluent and the conduit, wherein the second inert diluent is in fluid communication with the conduit between the closed loop reactor and the first valve; where, when the first valve is opened and the second valve is closed, the third valve opens, allowing the second inert diluent to enter the conduit.
15. 15. A process for purging polymeric solids from a conduit connected to a closed-loop reactor and in fluid communication with the closed-loop reactor, comprising the steps of: closing a first valve in response to a first signal from a first sensor , where the first valve is connected to and in fluid communication with the conduit; opening a second valve in response to a second signal from a second sensor, where the second valve is in fluid communication between a first inert diluent and the conduit, and where the first inert diluent is in fluid communication with the conduit between the reactor closed circuit and the first valve; flowing sufficient quantities of the first inert diluent under sufficient pressure into the conduit to purge polymeric solids from the conduit.
16. 16. The process of claim 15, wherein the first and second sensors are equal.
17. 17. The process of claim 15, wherein the first and second signals are equal.
18. 18. An apparatus for returning fine particles to a polymerization slurry in a closed-loop reactor, comprising: a discharge valve for discharging a portion of the polymerization slurry from the closed-loop reactor to a first transfer conduit; the first transfer conduit communicating said polymerization slurry therein to a first flash tank, the first flash tank converting a portion of the polymerization slurry into a first fluid, the first fluid comprising a diluent and the fine particles; a second transfer conduit communicating the first fluid therein to a first cyclonic separator, the first cyclonic separator converting a portion of the first fluid into a second fluid comprising the diluent and the fine particles; a third transfer conduit that communicates the second fluid to a heat exchanger, the heat exchanger converting the second fluid into a liquid comprising the diluent and the fine particles; and a fourth transfer conduit that communicates the liquid to the polymerization slurry in the closed loop reactor.
19. The apparatus of claim 18, further comprising a heater for the first transfer conduit for heat exchange between the heater for the first transfer conduit and the polymerization slurry.
20. 20. A process for returning fine particles to a polymerization slurry in a closed-loop reactor, comprising the steps of: discharging a portion of the polymerization slurry from the closed loop reactor; communicating the discharge polymerization slurry to a first flash tank; converting in the flash tank a first portion of the polymerization slurry in a first fluid, the first fluid comprising a diluent and the fine particles; communicating the first fluid of the first flash tank to a first cyclone separator; converting in the cyclone separator a portion of the first fluid in a second fluid comprising the diluent and the fine particles; communicating the second fluid to a heat exchanger; converting in the heat exchanger the second fluid into a liquid comprising the diluent and the fine particles; and returning the liquid to the polymerization slurry in the closed loop reactor.
21. 21. A process for producing polymer from a polymerization slurry in a closed-loop reactor operating at a space-time yield greater than 2.8 lbs / hr-gal, comprising the steps of: • forming the polymer in the slurry of polymerization, wherein the polymerization slurry comprises a liquid and solid medium; discharge the polymerization slurry through a discharge valve to a first transfer conduit, the polymerization slurry, after the discharge, referred to as # a polymerization effluent; heating the polymerization effluent in said first transfer conduit at a temperature below the melting temperature of the polymer; communicating said polymerization effluent through said first transfer conduit to a first flash tank, wherein the pressure in said first flash tank and the temperature of said heated polymerization effluent are such as to produce a vapor of about 50. to about 100% of the liquid medium; 0 condensing the vapor obtained in the first flash step by heat exchange; discharging said first solid polymer flash tank to a second flash tank through a seal chamber of sufficient dimensions to maintain a volume of polymer solids in said seal chamber sufficient to maintain a pressure seal; communicate the polymer solids to a second flash tank; Exposing the polymer solids to a pressure reduction of a higher pressure in the first flash tank at a lower pressure in said second flash tank; and discharging the polymer solids from said second flash tank.
22. 22. The process of claim 21, wherein the • Weight percentage of the solids in the polymerization slurry is greater than 47%.
23. 23. The process of claim 21, wherein the closed-loop reactor is operating at a circulating pumping head / reactor length ratio greater than 0.15 5 ft / ft.
24. 24. The process of claim 21, wherein the closed loop reactor is operating with a recirculation pumping head greater than or equal to 200 ft.
25. 25. The process of claim 21, wherein the polymerization slurry is circulated within the closed-loop reactor by multiple pumps and where the volume is greater than 20,000 gallons.
26. 26. The process of claim 21, wherein the closed loop reactor has more than eight vertical legs.
27. 27. The process of claim 21, wherein the heat exchange in the condensation step is accomplished with a heat exchanger equipped with a temperature controlled heat transfer medium.