Advanced Powder Technology, Vol.15, No.1, 79-96, 2004
Statistical and power spectral analysis of quality of fluidization for different particle size distributions at high temperature
Previous studies have shown the effect of many parameters on the operation of a fluidized bed at room temperature, but have not considered the effect of the particle size distribution of bed materials or high temperature. This investigation examines how the high temperature and particle size distributions affect the quality of fluidization. Good quality is regarded as uniformly expressed fluid velocity across through the fluidized bed. Four particle size distributions of silica were fluidized in air at atmospheric pressure, from 500 to 800degreesC. The evaluated particle size distributions included a narrow cut, a binary mixture, a uniform distribution and a Gaussian distribution. During an experiment, the pressure fluctuations were measured, and then the statistical and power spectrum analyses were performed to assess the quality of fluidization in the fluidized bed. According to the resulting mean amplitude, dominant frequency and fluidization index, the sand bed displays the best quality of fluidization at 1.3U(mf) in most cases. When the static bed height is controlled at the shallow bed, the quality of fluidization is highest and the effects of temperature on the four particle distributions are not obvious. Increasing the static bed height causes the influence of temperature to become gradually apparent. The mean amplitude and fluidization index decrease as temperature increases, implying an increase in the quality of fluidization. In all cases, increasing the static bed height causes differences between the four distributions to become gradually apparent, The mean amplitude and index of the narrow distribution are smallest, indicating the fluidization is best. However, the Gaussian distribution shows a similarly narrow behavior. For flat and binary distributions, differently sized components of sand compete in terms of segregation and mixing, affecting the behavior of fluidization, so that both of them belong to the same behavior of fluidization.