Flow Characteristics Investigation Of Gas Liquid Solid Exterior Circulation Fluidized Bed

The pressure drop along the steady fluidization segment in the outer circulating fluidized bed was investigated. It showed that the pressure drop was affected by the superficial liquid velocity, superficial gas velocity, solid volume content and average particles' diameter. Then the formula of pressure drop through the unit bed height was given. It indicated that the influence of superficial liquid velocity and the average particles' diameter was more evidence.The onset velocity was an important parameter that affected the normal operation of the gas liquid solid outer circulating fluidized bed. The onset velocity was determined by the trend of pressure drop changing with the liquid velocity. By experimental investigation, the effects of average particle diameter, solid volume content and superficial gas velocity on the onset velocity were reviewed. It indicated that the onset velocity of the outer circulating fluidized bed should be much larger than the terminal velocity of single particle, which was increasing with the solid volume content and diameter of the particles's increasing. The onset velocity with gas added was larger than that without gas added when the solid volume content is small, the onset velocity with gas added was almost the same as that without gas added when the solid volume content was greatThe pressure fluctuation was an important information that could be used to indicate the dynamic characteristics of the fluidized bed. So the flow characteristics of gas liquid solid outer circulating fluidized bed were investigated by the pressure fluctuation signals. The statistics analysis, frequency analysis and correlation analysis were made with the wall pressure fluctuations signals. The statistics and amplitude spectrum analysis indicated that the pressure fluctuation characteristics were similar at steady fluidization segment. The probability density function was close to the normal distribution. The power spectrum density analysis indicated that the power distribution frequency range generated because of the liquid flow and the motion of the particles concentrated in 0-10Hz and 30~40Hz in the liquid solid fluidized bed. After the gas entered into the bed, the signal power was signally focused in the 0-15Hz, that was to say that the pressure fluctuation was dominated by air bubbles. The correlation analysis indicated that the pressure fluctuation signals exist between periodic signals and random signals.