Study On Fluidized Bed Reactor For Gas-phase Propylene Polymerization

The improvement of the catalyst chemistry and process technology has simplified the polypropylene process with environmental friend. The development of the process, based on agitated fluidized bed and circulating fluidized bed reactor, has reduced invest and operating costs with high polymer properties.This thesis aimed at the research on the engineering aspects of the agitated fluidized bed and circulating fluidized bed reactor technology, especially the fluid hydrodynamics was investigated.The pressure fluctuation signals at different rotation speeds of stirrer blade and gas velocities are analyzed with statistics analysis and power spectrum analysis. Experimental results indicate that the rotation of impeller blades do not affect the minimum fluidization velocity U_mf, but made Geldart B and D particles appear particulate fluidization due to the rotation of impeller blade. The minimum bubbling velocity U_mb increases with the increasing rotation speeds of impeller blade, and U_mb/U_mf correlated with the rotation speed, N, only.The pressure fluctuation signals in the agitated fluidized bed were decomposed into 9 scales by Dau2 wavelet. It shows that the wavelet energy characteristics of scale 1 detail signal changed sharply in a range of gas velocity, then a criterion of the minimum bubbling velocity and full bubbling velocity is developed. The minimum bubbling velocity and full bubbling velocity increases lineally with the increasing rotation speeds of impeller blade, while the fluidized bed transits from the bubbling fluidization regime to the particulate fluidization regime.This thesis also reported fundamental observations of the superficial gas velocity and solid-circulation flux in riser, G_s, effect on the fluidization properties of the fluidized bed. The observations disclosed that there is a single major frequency in the power spectrum density figure when the G_s are low. The multi-scale analysis indicated that the movement of gas-solid fluid system to the boundary of equipment in the circulating fluidized bed is larger than that in the agitated fluidized bed.The diameter of polymer particles is so large that the particle velocity is small, which result in the mean residence time of solid is long. Meanwhile, the radial distribution of particle velocity is less uniform, consequently, the tailing appearance of residence time distribution become very serious.