Determination of the solid concentration in a binary mixture from pressure drop measurements

Abstract

A new and simple method to estimate the concentration of solids in a binary solids mixture is proposed and experimentally tested in a small fluidized bed set up. In the proposed method, it is necessary to measure the pressure drop in different sections of the bed at different gas velocities so as to be able to determine local minimum fluidization velocities using the Ergun equation. Because the minimum fluidization velocity of a solids mixture is known to be dependent on its weight fraction, a calibration curve can be derived by means of the Cheung equation and this is shown to be sufficient to obtain reasonably good estimates of the axial solids concentration profiles inside the bed. This methodology has been applied to three different mixtures of iron oxide ore of varying size with limestone or glass spheres. Satisfactory agreement between the experimental and calculated concentrations as well as pooled relative standard deviations lower than ±7%, are obtained in all three cases. This technique could facilitate future experimental research on solids mixing and segregation phenomena in fluidized beds, as it is a very low-cost, non-destructive and very fast method to determine solids concentration bed profiles.