روح اله فاتحی

Today the use of fluidized bed reactor for the production of polyethylene due to its characteristics of heat and mass transfer, is more common than other existing processes. These reactors are not fault-free. Electrostatic charge generation from particle–particle and particle–wall contacts in gas–solid fluidized beds is virtually unavoidable and generally undesired. This causes that particles adhere to the walls of the reactor and if the operational conditions are close to the melting point of the polymer, it creates a layer on the wall and finally the reactor will be out of service. In this study, a multifluid Eulerian model using computational fluid dynamics (CFD) with electrostatic model taken into account is used to achieve the electrostatic effect on the dynamics of fluidized bed. At first the hydrodynamic simulation for fluidized bed containing solid particles of the same size without the effects of electrostatic charge was performed. In this case bed expansion ratio was obtained 1.62 (u/umf=1.5). For fluidized bed containing solid particles with three different size ranges, bed expansion was obtained 0.43 m (u/umf=1.5)). In the following to obtain the order of magnitude of electric potential generated due to charged particles contained in square domain, According to the type of particles charges this value is negative and in order of 104. Finally for semi-industrial reactor containing charged particles in three different size ranges, bed expansion (u/umf=1.5) and the oreder of magnitude of electric potential were obtained 0.43 m and 104 respectively. In this case the height of layers made in the wall is equal to 0.32 m.