| This dissertation describes computational fluid dynamics (CFD) simulations of olefin polymerizations in a rotating fluidized bed. The commercial code, FLUENT, is used to achieve this goal.; Low-pressure gas phase polymerization is widely used for polymerization of Ethylene and Propylene in the fluidized bed reactors. In spite of the significant application of this kind of reactors, they have shown limited flexibility in achieving high gas throughput because of the possibility of slugging and the inability to provide suitable heat transfer rates. To overcome these disadvantages and enhance the efficiency of the fluidized reactors, the feasibility of using the rotating fluidized bed reactors for this purpose is studied.; In rotating fluidized bed by applying high rotational speed and creating a radial acceleration much stronger than gravity, one can achieve more gas throughput without serious formation of bubbles or slugging bed and the heat transfer rate will be improved.; To study the dynamic behavior of a gas-solid mixture in a rotating fluidized bed, a cylindrical reactor with porous wall connecting to a draft tube located on the top of the reactor was considered. The solid particles initially were placed at the bottom of the reactor and gas enters the reactor from the porous wall. Polyethylene particles (200 mum) and air were used as solid and gas phase respectively. Two dimensional axisymmetry, transient and isothermal flows, with no chemical reaction were assumed. Also the effects of pressure and particle size on the gas-solid flow were predicted.; In the second phase of this study, the particle size distribution that exists in the polymerization reaction is characterized by two solid phases, 200 mum and 1000 mum, which are representing the prepolymerized and final polymer product sizes accordingly. The hydrodynamics of the mixture of these particles were calculated and the numerical results revealed that when the densities of the particles are the same, the smaller particles leave the reactor with the lower gas inlet velocity, while the big particles remain closer to the side inlet distributor.; In the last section of this study, the effect of continuous particle size, which occurs in any polymerization reaction, on the flow behavior has been investigated. Coupling the population balance equation, which gives the transient particle size distribution, with continuity and momentum equations is providing the valuable information regarding the flow pattern in these kinds of systems. |
