Solid-fluid mixing behavior of conical spouted beds with internal devices

Abstract

The effect of draft tubes and fountain confiner on the gas and solids mixing behavior is studied in conical spouted beds. Accordingly, the bed porosity has been determined in different hydrodynamic regimes of 1:1; 1:25 and 1:5 u=ums , with beds equipped with draft tubes of 0%; 56% and 100% opening ratio. These devices significantly affect the gas residence time and particle cycle time distributions, which are further improved by using a fountain confiner, specially when high inlet gas flow rates are desired. The addition of this device was found to remove stagnant gas pockets over the annular zone, while reducing the par- ticle cycle time by 15% with the OSDT configuration at 1:5 u=u ms . This reduction heavily depends on the distance between the bed surface and the fountain confiner. By including draft tubes, the expected par- ticle cycle time can be more than doubled due to the reduced annular-spot solids circulation. Therefore, it was found that a combination of internal devices and operating flow rate present a promising strategy to control the gas flow pattern, while keeping the distribution of particles cycle times required for each application.