Fluidization behavior of polymeric particles in gas—solid fluidized beds

Abstract

A systematic study is conducted which illustrates the effects of the average size and size distribution of polymeric particles on the fluidization quality of gas—solid fluidized beds. The fluidization quality is characterized by the bubble flow rate, and evaluated based on a bed collapse technique. Polymeric particles used include polyethylene (PE) and polypropylene (PP) resins with a density of 0.66 and 0.57 g/cm 3, respectively, and sizes ranging from 116–775 μm. The results indicate that there is virtually no effect of the particle size and its distribution on the fluidization quality for PE and PP particles of Geldart group B, provided that the fluidization quality is characterized by the bubble flow rate. These results are consistent with Geldart's finding (Geldart, 1972). For PE particles belonging to Geldart group A, it is found that the particle size has a slight effect on the fluidization quality. However, the size of group A PP particles and the size distribution of group A PE particles have essentially no effect on the fluidization quality. Experiments involving mixing fine polyethylene powders (microthene), having an average size of 32 μm (Geldart group C), with PE particles are also conducted to investigate the fine particle—coarse particle interactions, such as the van der Waals and electrostatic forces, in the fluidized bed. The improvement of the fluidization quality due to the addition of fine powders in a bed of polymeric particles is discussed in the light of the observation of surface structures from an SEM study of the mixture sampled from the fluidized bed.