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A polymerization loop reactor including a loop reaction zone, a continuous takeoff, and a fluid slurry disposed in the reaction zone. A generally cylindrical wall defines the loop reaction zone. The length of the loop reaction zone and the nominal outside diameter of the generally cylindrical wall d

A polymerization loop reactor including a loop reaction zone, a continuous takeoff, and a fluid slurry disposed in the reaction zone. A generally cylindrical wall defines the loop reaction zone. The length of the loop reaction zone and the nominal outside diameter of the generally cylindrical wall define a length/diameter ratio greater than 250. The reactor can be charged with a fluid slurry including an olefin monomer reactant, solid olefin polymer particles, and a liquid diluent. The concentration of the solid olefin polymer particles in the slurry can be greater than 40 weight percent based on the weight of polymer particles and the weight of liquid diluent. Also disclosed is a polymerization process carried out by polymerizing, in the loop reaction zone of a reactor as defined above, at least one olefin monomer in a liquid diluent to produce a fluid slurry as defined above.

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That which is claimed is: 1. A polymerization loop reactor comprising: a loop reaction zone configured to polymerize an olefin monomer into a polyolefin in the presence of a diluent and defined by a generally cylindrical wall having a nominal outside diameter of at least 22 inches (55 cm), wherein

That which is claimed is: 1. A polymerization loop reactor comprising: a loop reaction zone configured to polymerize an olefin monomer into a polyolefin in the presence of a diluent and defined by a generally cylindrical wall having a nominal outside diameter of at least 22 inches (55 cm), wherein a length/diameter (L/D) ratio of the generally cylindrical wall is in the range of 700 to about 1500; an impeller disposed within the loop reaction zone within a casing portion of the generally cylindrical wall, the casing portion having a first inside diameter, and the remaining portion of the cylindrical wall having at least a second inside diameter, wherein the first inside diameter is larger than the second inside diameter; and a continuous take off (CTO) positioned along the generally cylindrical wall and configured to substantially continuously withdraw a discharge slurry having a solids concentration greater than an average solids concentration of the slurry circulating through the loop reaction zone. 2. The polymerization loop reactor of claim 1, wherein the solids concentration of the discharge slurry is greater than 50 weight percent. 3. The polymerization loop reactor of claim 1, wherein a flow path of the CTO is configured substantially tangential to a curvature of an elbow of the generally cylindrical wall. 4. The polymerization loop reactor of claim 1, wherein a diameter of the impeller is at least as large as the second inside diameter of the generally cylindrical wall. 5. The polymerization loop reactor of claim 1, wherein the casing portion of the generally cylindrical wall has a first nominal outside diameter and the remaining portion of the generally cylindrical wall has at least a second nominal outside diameter, wherein the first nominal outside diameter is larger than the second nominal outside diameter. 6. The polymerization loop reactor of claim 5, wherein the first nominal outside diameter is at least about 2 inches larger than the second nominal outside diameter. 7. The polymerization loop reactor of claim 6, wherein the impeller is sized to circulate at least about 34,000 gallons per minute (gpm) of the slurry through the loop reaction zone. 8. The polymerization loop reactor of claim 1, wherein the nominal outside diameter is about 24 inches (57 cm), about 26 inches (66 cm), about 28 inches (70 cm), or about 30 inches (76 cm). 9. The polymerization loop reactor of claim 1, wherein a size and a geometry of the impeller are configured to provide for circulation of the slurry through the loop reaction zone at a velocity greater than the saltation velocity of the slurry. 10. The polymerization loop reactor of claim 1, wherein the loop reactor zone has a volume of at least 22,000 gallons (84 m3) . 11. The polymerization loop reactor of claim 1, wherein the loop reactor zone has a volume of at least 40,000 gallons (152 m3 ). 12. The polymerization loop reactor of claim 1, wherein the loop reactor zone has a volume at least 45.000 gallons (76 m3). 13. The polymerization loop reactor of claim 1, wherein the loop reactor zone has a volume of greater than 30,000 gallons (114 m 3). 14. The polymerization loop reactor of claim 1, wherein an average solids concentration of the slurry circulating through the loop reaction zone is greater than about 50 weight percent. 15. The polymerization loop reactor of claim 1, wherein the CTO is configured to facilitate pressure control of the loop reaction zone. 16. A polymerization loop reactor comprising: a loop sluny reactor configured to polymerize olefin into polyolefin, and comprising: a reaction zone having a volume of at least about 22,000 gallons and defined by a generally cylindrical wall having a nominal outside diameter of at least 22 inches (55 cm), wherein a ratio of a length of the loop reaction zone to the nominal outside diameter is in the range of 700 to about 1500; an in-line impeller disposed in the reaction zone, wherein a first inside diameter of a casing portion of the generally cylindrical wall surrounding the in-line impeller is larger than a second inside diameter of a remaining portion of the generally cylindrical wall, wherein the in-line impeller and associated motor are configured to circulate a polyolefin slurry through the loop reaction zone at a velocity greater than a saltation velocity of the slurry; and a continuous take off (CTO) configured to substantially continuously withdraw the slurry from the loop reaction zone and to facilitate pressure control of the loop reaction zone. 17. The system of claim 16, wherein a first nominal outside diameter of the casing portion is greater than a second nominal diameter of the remaining portion by at least about 2 inches. 18. A polymerization loop reactor comprising: a loop reaction zone configured to polymerize olefin into a polyolefin, and defined by a generally cylindrical wall having a nominal outside diameter of at least 22 inches, wherein the length of the loop reaction zone and the nominal outside diameter of the generally cylindrical wall define a length/diameter ratio in the range of 700 to about 1500; an in-line axial pump comprising an external motor, a casing, and an in-line impeller disposed within the casing, the casing having a casing nominal outside diameter at least about 2 inches larger than the nominal outside diameter of the generally cylindrical wall; and a plurality of continuous take offs configured to continuously withdraw a fluid slurry from the loop reaction zone. 19. The polymerization loop reactor of claim 18, wherein a diameter of the impeller is at least as large as an inside diameter of the generally cylindrical wall. 20. A polyethylene production system comprising: a loop slurry reactor comprising: a loop reaction zone configured to polymerize ethylene into polyethylene and defined by a generally cylindrical wall having a nominal outside diameter of at least 22 inches, wherein the length of the loop reaction zone and the nominal outside diameter of the generally cylindrical wall define a length/diameter ratio in the range of 700 to about 1500; an impeller configured to circulate a slurry through the loop reaction zone at a velocity greater than a saltation velocity of the slurry, wherein the slurry comprises polyethylene solid particles in a liquid diluent, and the velocity is at least 32 feet per second; and a continuous take off (CTO) configured to substantially continuously withdraw a discharge slurry from the loop reaction zone and to facilitate pressure control of the loop reaction zone, wherein the CTO is positioned along the generally cylindrical wall to so that the discharge slurry has a solids concentration higher than an average solids concentration of the circulating slurry; and a flash chamber configured to receive the discharge slurry and to vaporize liquid diluent in the discharge slurry. 21. The polyethylene production system of claim 20, wherein the impeller comprises at least two impeller disposed in series in the loop reaction zone.