Improved digital image analysis technique for the evaluation of segregation in pseudo-2D beds

• A new Digital Image Analysis technique has been developed.
• The technique detects particle types with unique colors.
• The technique can evaluate bed height, and bubble sizes and positions.
• Axial segregation for binary systems was determined within 5% accuracy.
• The new technique was verified with DEM model results.

In addition to information on the behavior of bubbles, the dynamics of mixing and segregation is often required because of its importance in describing physical and chemical processes involving fluidized suspensions. In this work, the enhanced capacities of state-of-the-art photographic instruments have been adopted in a new Digital Image Analysis (DIA) technique for the evaluation of local compositions and degrees of segregation in lab-scale pseudo-2D gas–solid fluidized beds. Furthermore, the newly developed image analysis technique permits the simultaneous evaluation of bed height and bubble size and position. The extent of mixing and segregation for polydisperse systems can be determined more accurately when the different particle species are classified by distinct colors. The reproducibility of lab measurements was found to be satisfactory, and the extents of segregation in snapshots of a Discrete Element Method (DEM) simulation, evaluated using the new technique, were found to be in good agreement with exact values calculated from individual particle positions in the DEM.

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