Effect of operating conditions on the hydrodynamics in fountain confined conical spouted beds

Abstract

Spouted bed stability and operation is greatly affected by particle features. Accordingly, the hydrodynamic behaviour of conical spouted beds has been studied for fine particles differing in size and density in a wide range of inlet air flow rates. This knowledge is essential for a successful scaling up and industrial implementation of the spouted bed. Therefore, the effect air velocity and solid properties (density and size) have on local solid velocity has been ascertained in a fountain confined conical spouted bed using a borescope technique (Particle Tracking Velocimetry, PTV) applied to several bed configurations. The results show a close relationship between the inlet air velocity and the local solid velocity, with the gas-solid contact being especially vigorous in the configurations without draft tube and with the open-sided draft tube. The solid circulation flow rate is lowest when a nonporous draft tube is used due to the low solid vertical velocities in the annulus, even at high air flow rates. Nevertheless, vertical velocities in the annular zone increase when particle size and density are increased, although these velocities are lower in the spout and fountain regions due to the higher momentum exchange required for their acceleration.