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An olefin polymerization process and apparatus wherein a fluid slurry comprising monomer, diluent and catalyst is circulated in a continuous loop reactor by two or more pumps. The process and apparatus allow operating the reaction at significantly higher solids content in the circulating fluid slurr

An olefin polymerization process and apparatus wherein a fluid slurry comprising monomer, diluent and catalyst is circulated in a continuous loop reactor by two or more pumps. The process and apparatus allow operating the reaction at significantly higher solids content in the circulating fluid slurry. In a preferred embodiment, the fluid slurry is circulated by two impellers arranged so that the downstream impeller benefits from the rotational energy imparted by the upstream impeller. An olefin polymerization process operating at higher reactor solids by virtue of more aggressive circulation has improved efficiencies, particularly in larger-volume reactors.

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What is claimed is: 1. A loop reactor apparatus comprising: a plurality of major segments; a plurality of minor segments; wherein each of the major segments is connected at a first end to one of the minor segments, and is connected at a second end to another of the minor segments, such that the maj

What is claimed is: 1. A loop reactor apparatus comprising: a plurality of major segments; a plurality of minor segments; wherein each of the major segments is connected at a first end to one of the minor segments, and is connected at a second end to another of the minor segments, such that the major and minor segments form a continuous flow path adapted to convey a fluid slurry; at least two pumps for imparting motive force to the fluid slurry within the reactor, each pump operably connected to an impeller disposed in the continuous flow path; wherein two of the impellers face each other and rotate in opposite directions and the two impellers are spaced sufficiently close so that one of the impellers benefits from the rotational energy of the other of the impellers; means for introducing an olefin monomer into the continuous flow path; means for introducing a diluent into the continuous flow path; means for introducing a polymerization catalyst into the continuous flow path; and means for removing a portion of a fluid slurry from the continuous flow path. 2. A loop reactor apparatus according to claim 1 wherein the two impellers are disposed in the same segment. 3. A loop reactor apparatus according to claim 1 wherein a portion of the continuous flow path upstream of at least one of the impellers houses at least one guide vane arranged to impart rotational motion in a direction opposite to the rotational motion of the impeller. 4. A loop reactor apparatus according to claim 1 wherein at least one impeller is situated in an enlarged section of one of the segments, and the enlarged section and the at least one impeller have diameters greater than a diameter of the segments. 5. A loop reactor apparatus according to claim 1 wherein at least one impeller and the segment which houses the impeller define a clearance, and the clearance is 1/16 inch or less. 6. A loop reactor apparatus according to claim 5 wherein the clearance is 1/64 inch or less. 7. A loop reactor apparatus according to claim 1 wherein each impeller has a diameter greater than the average diameter of the segments. 8. A loop reactor apparatus according to claim 1 wherein each impeller consists of a material selected from the group consisting of titanium, aluminum and steel. 9. A loop reactor apparatus according to claim 1 wherein each impeller is a solid mass of metal having no substantial voids. 10. A loop reactor apparatus according to claim 1 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 30,000 gallons or more. 11. A loop reactor apparatus according to claim 1 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 33,000 gallons or more. 12. A loop reactor apparatus according to claim 1 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 35,000 gallons or more. 13. A loop reactor apparatus according to claim 1 wherein the major segments are vertical. 14. A loop reactor apparatus according to claim 1 wherein the major segments are horizontal. 15. A loop reactor apparatus comprising: a plurality of major segments; a plurality of minor segments, each minor segment connecting two of the major segments to each other, whereby the major and minor segments form a continuous flow path; a monomer feed attached to one of the segments; a catalyst feed attached to one of the segments; a product take-off attached to one of the segments; an upstream pump and a downstream pump, wherein the pumps each are attached to an impeller disposed in the interior of the continuous flow path, and the pumps are arranged so that the impellers rotate in opposite directions and are sufficiently close so that the rotational energy imparted by the upstream pump is at least partially recovered by the downstream pump; wherein the impellers are situated in at least one enlarged section of one of the segments, the enlarged section and the impellers having diameters greater than diameter of the segments. 16. A loop reactor apparatus according to claim 15 wherein the two impellers are disposed in the same segment. 17. A loop reactor apparatus according to claim 15 wherein a portion of the continuous flow path upstream of at least one of the impellers houses at least one guide vane arranged to impart rotational motion in a direction opposite to the rotational motion of the impeller. 18. A loop reactor apparatus according to claim 15 wherein at least one impeller is situated in an enlarged section of one of the segments, and the enlarged section and the at least one impeller having diameters greater than a diameter of the segments. 19. A loop reactor apparatus according to claim 15 wherein at least one impeller and the segment which houses the impeller define a clearance, and the clearance is 1/16 inch or less. 20. A loop reactor apparatus according to claim 19 wherein the clearance is 1/64 inch or less. 21. A loop reactor apparatus according to claim 15 wherein each impeller has a diameter greater than the average diameter of the segments. 22. A loop reactor apparatus according to claim 15 wherein each impeller consists of a material selected from the group consisting of titanium, aluminum and steel. 23. A loop reactor apparatus according to claim 15 wherein each impeller is a solid mass of metal having no substantial voids. 24. A loop reactor apparatus according to claim 15 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 30,000 gallons or more. 25. A loop reactor apparatus according to claim 15 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 33,000 gallons or more. 26. A loop reactor apparatus according to claim 15 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 35,000 gallons or more. 27. A loop reactor apparatus comprising: a plurality of major segments; a plurality of minor segments, each minor segment connecting two of the major segments to each other, whereby the major and minor segments form a continuous flow path; a monomer feed attached to one of the segments; a catalyst feed attached to one of the segments; a product take-off attached to one of the segments; at least one guide vane disposed within the continuous flow path; and a pump, wherein the pump is attached to an impeller disposed in the interior of the flow path downstream of the guide vane, wherein the guide vane and the impeller impart rotational motion on the flow path in opposite directions and are sufficiently close so that the slurry is engaged in rotational motion upon engaging the downstream pump. 28. A loop reactor apparatus according to claim 27 wherein at least one impeller is situated in an enlarged section of one of the segments, and the enlarged section and the at least one impeller having diameters greater than a diameter of the segments. 29. A loop reactor apparatus according to claim 27 wherein at least one impeller and the segments which houses the impeller define a clearance,and the clearance is 1/16 inch or less. 30. A loop reactor apparatus according to claim 29 wherein the clearance is 1/64 inch or less. 31. A loop reactor apparatus according to claim 27 wherein each impeller has a diameter greater than the average diameter of the segments. 32. A loop reactor apparatus according to claim 27 wherein each impeller consists of a material selected from the group consisting of titanium, aluminum and steel. 33. A loop reactor apparatus according to claim 27 wherein each impeller is a solid mass of metal having no substantial voids. 34. A loop reactor apparatus according to claim 27 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 30,000 gallons or more. 35. A loop reactor apparatus according to claim 27 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 33,000 gallons or more. 36. A loop reactor apparatus according to claim 27 wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 35,000 gallons or more. 37. A loop reactor apparatus according to claim 27 wherein the major segments are vertical. 38. A loop reactor apparatus according to claim 27 wherein the major segments are horizontal. 39. A loop reactor apparatus comprising: a plurality of major segments; a plurality of minor segments, each minor segment connecting two of the major segments to each other, whereby the major and minor segments form a continuous flow path for carrying slurry; a monomer feed attached to one of the segments; a catalyst feed attached to one of the segments; a product take-off attached to one of the segments; a pump within an arced pump case, the pump case being positioned in one of the segments, the pump having at least one impeller mounted on a shaft, the impeller having blades that are oriented at an angle between 0 to 90 degrees to the shaft, the pump having a bulge positioned along the shaft proximate the at least one impeller, such that a curved flow path is defined between the bulge and the pump case, the flow path being disposed such that the slurry flows by the blades and is redirected out of the pump case by the flow path. 40. A loop reactor apparatus according to claim 39, further including guide vanes situates along the flow path to redirect the rotational flow of the slurry upon discharge from the impeller. 41. A loop reactor apparatus according to claim 39, further including a second pump having an impeller opposite the pump, wherein the impellers of the pumps face each other and rotate in opposite directions and the impellers are spaced sufficiently close so that one of the impellers benefits from the rotational energy of the other of the impellers. 42. A loop reactor apparatus according to claim 41, wherein at least one of the impellers is situated in at least one enlarged section of one of the segments, and the enlarged section and the impeller situated therein have diameters greater than the diameter of the segments. 43. A loop reactor apparatus according to claim 39, wherein the pump is a mixed pump having at least two impellers. 44. A loop reactor apparatus according to claim 39, wherein a portion of the continuous flow path upstream of the impeller houses at least one guide van arranged to impart rotational motion in a direction opposite to the rotational motion of the impeller. 45. A loop reactor apparatus according to claim 39, wherein the impeller and the segment which houses the impeller define a clearance, and the clearance is 1/16 inch or less. 46. A loop reactor apparatus according to claim 39, wherein the impeller has a diameter greater than the average diameter of the segments. 47. A loop reactor apparatus according to claim 39, wherein the impeller consists of a material selected from the group consisting of titanium, aluminum and steel. 48. A loop reactor apparatus according to claim 39, wherein the impeller is a solid mass of metal having no substantial voids. 49. A loop reactor apparatus according to claim 39, wherein the loop reactor apparatus defines a reactor volume, and the reactor volume is 50,000 gallons or more. 50. A loop reactor apparatus according to claim 39, wherein the major segments are vertical. 51. A loop reactor apparatus according to claim 39, wherein the major segments are horizontal.