segregation behaviour of particles in gas solid fluidized beds at elevated pressure

a comprehensive mathematical model based on the discrete particle model and computational fluid dynamics was utilized to investigate mixing and segregation of particles in fluidized beds at high pressure. to quantify the extent of mixing in the bed, the lacey mixing index was used. simulations were carried out with different mass fractions of small particles at various pressures ranging from 1 to 64 bar and at various superficial gas velocities. the results showed that the bed transforms from a segregated state to a fully mixed condition when the operating pressure is increased. vertical segregation of particles at low pressure was replaced by horizontal segregation of particles at high pressures in which small particles were collected mainly near the walls and large particles at the center of the bed. at the same pressure, the rate of segregation decreased with increasing the mass fraction of small particles.