Characterization of Fluidization and Segregation of Biomass Particles by Combining Image Processing and Pressure Fluctuations Analysis

Bed segregation is inevitable in biomass-sand fluidized beds because of density and size differences, but segregation pattern can be significantly different under various operational conditions. In the present work, the combination of image processing technology and pressure fluctuations analysis is used to investigate the fluidization and segregation. Experiments have been carried out in a 3D fluidized bed. The biomass material studied is cotton stalk. Two groups of binary systems are considered, obtained by mixing sand with biomass particles of different sizes and/or concentrations. In addition, the bed-frozen method is also adopted to examine the segregation degree. It is found that the transition velocity from bubbling to turbulent fluidization regime decreases with the increase of biomass size and concentration. The results also show that the biomass concentration has little influence on the segregation degree, and the biomass size significantly affects the rate of segregation, which increases with the size. The pressure gradient and standard deviation of pressure fluctuation are demonstrated to be useful for indicating the bed segregation, which are validated by the result by the bed-frozen method.