Gas phase production of polyethylene
Methods for producing a polymer include contacting at least one monomer under polymerization conditions with a fluidized bed of a polymerization catalyst on a particulate support; measuring a plurality of pressures of the fluidized bed at a plurality of locations corresponding to increasing heights from a bottom of the fluidized bed; calculating a plurality of pressure drops between the plurality of locations based on the measured pressures; performing a regression analysis on the calculated plurality of pressure drops; correlating the plurality of pressure drops to corresponding heights from the bottom of the fluidized bed based on the regression analysis; determining a height of the fluidized bed based on the correlating; and controlling polymerization conditions based on the determined height of the fluidized bed. The method can also be used to detect malfunctioning pressure transducers based on deviation between measured and expected values.
1 . A process for producing a polyolefin comprising:
(a1) contacting at least one olefin monomer under polymerization conditions with a fluidized bed of a polymerization catalyst on a particulate support, the bed having a bottom and a top;
(a2) measuring the pressure at a plurality of different locations along the fluidized bed at increasing heights above the bottom, and below the top, of the bed;
(a3) using the pressure measurements obtained in (a2) to calculate the pressure drop between adjacent locations along the bed;
(a4) applying regression analysis to the calculations generated in (a3) to determine the variation in pressure drop with height above the bottom of the bed;
(a5) extrapolating the variation in pressure drop with bed height to determine the total height of the bed; and
(a6) controlling the polymerization conditions based at least in part upon the total bed height determined in (a5).
2 . The process of claim 1 , wherein controlling the polymerization conditions comprises maintaining the fluidized bed within a desired range of fluidized bed height.
3 . The process of claim 1 , wherein the polymerization catalyst comprises a metallocene, and/or the at least one olefin monomer comprises ethylene.
4 . The process of claim 1 , wherein the regression analysis applied in (a4) is linear.
5 . The process of claim 1 , wherein the regression analysis applied in (a4) is polynomial.
6 . The process of claim 5 , wherein the regression analysis applied in (a4) is second degree polynomial.