The influence of the experimental span of Time-resolved X-ray tomography on dynamic parameters in a fluidized bed

Abstract

Fluidized beds have presented some problems to experimentalists in the past due to their opaque nature [1]. This problem has however been overcome by non-intrusive nor invasive measurement techniques. X-rays or Gamma rays can move through such systems where light (low energy radiation) cannot. Tomographic techniques can thus also be used with nuclear methods and is generally referred to as nuclear densitometry [1]. Using Time-resolved X-ray tomography on a fluidized bed is a state of the art technique. The first data of such a system has been presented by [1]. With this technique being novel, a thorough investigation of the measurement scenarios has not been performed thus far. The current study will focus on the influence of the experimental span on the average bubble velocity, bubble frequency and bubble volume. The influence of thresholding was investigated and the accuracy of the obtained results will be determined by existing empirical equations. In all of the experiments, glass particles were used with a particle size distribution of 79-149 μm. In the present study the bed was fluidized using a single central jet and a porous plate distributer. This experimental set-up was chosen to make the study of the dynamic parameters more reliable and to include the uncertainties associated with a freely bubbling bed. The measurement technique is briefly discussed and it is concluded that at least 45 s is required to obtained a reliable result for the bubble velocity in a freely bubbling bed while at least 25 s are required to obtain reliable results for the bubble volume and frequency.