Industrially relevant Radioactive Particle Tracking study on the motion of adsorbent granules suspended in a pilot-scale water–air three-phase fluidized bed

The information obtained by one-dimensional Radioactive Particle Tracking is used to make an industrially relevant description of the macroscopic mixing of a three-phase bubble column. The objective is to characterize and compare the solid motion of granular activated carbon (d_p = 1 mm) and calcium alginate beads (d_p = 5 mm), widely used as adsorbents for pollutants and as support for catalysts, enzymes, and living organisms. The particles are suspended in water with upflowing air into a 0.1 m diameter and a 1 m height bubble column. The liquid–solid suspensions are in batch, and the air superficial velocity ranges within 0.01–0.12 m/s. The solid axial hold-up distribution of the carbon–water–air system is biased towards the bottom of the column, while the alginate–water–air system is more even. The axial dispersion coefficients obtained in both systems have a positive linear behavior within the operating range, which is uncannily marked in the carbon-water-air system, and it is an order of magnitude less than the alginate–water–air system. The contrasts of the two systems are mostly explained as a function of the solid densities. Axial mixing time distribution shows a sharp minimum at the second quartile of the column. Flow regime transition is assessed using information theory.