THE IMPACT OF FLUID-DYNAMICAL SCALING ON THE VERTICAL DISTRIBUTION OF SOLIDS IN BINARY FLUIDIZED BEDS

Paper i proceeding, 2025

A significant amount of the literature on the axial mixing and segregation of solids in fluidized beds consists of experimental studies carried out at ambient conditions, using solids utilized in the hot large-scale applications and fluidized with readily available gases. This practice disregards the effect of temperature on fluid-dynamics, limiting the validity of the results obtained. This work aims to assess the magnitude of the error committed when using such methodology, by comparing results from experiments regarding and disregarding fluid-dynamic scaling, referred to in this work as scaled and unscaled sets, respectively. A reference binary bed is considered for experiments, in which the bulk solids face corresponds to fine solids of type B, while the lean phase are fuel-like solids. The analysis focuses on the vertical distribution of the lean phase (measured by means of magnetic solids tracing) and bed dynamics (via pressure measurement). Results indicate that in the unscaled set, a significant portion of the lean solid phase is found in the freeboard, whereas the scaled set shows better distribution within the bed. This can be partially explained by the revealed differences in bed dynamics, with the unscaled bed exhibiting less frequent and larger bubbles compared to scaled set. These discrepancies lead to errors in timescales and hinder the accurate replication of bed dynamics in large-scale hot operations.