Investigation on hydrodynamics of triple-bed combined circulating fluidized bed using electrostatic sensor and electrical capacitance tomography

To investigate the hydrodynamics, a cold model of triple-bed combined circulating fluidized bed (TBCFB) has been built with an electrostatic sensor and a twin-plane electrical capacitance tomography (ECT) sensor. Experimental results show that with the increase in the superficial air velocity, the flow regime in the riser would transit from a dense plug flow to a core-annular flow, and finally to a dilute suspension flow. In the dense plug flow regime, the passage of the solids plugs in the riser can be monitored and the velocity measured using the twin-plane ECT sensor. In the core-annular flow regime, when the solids holdup is moderate, the measured solids velocities by the electrostatic sensor and the ECT sensor are comparable and complementary. With a dilute suspension flow in the riser, a homogeneous flow is observed with a nearly flat velocity profile of solid particles. On the contrary, in the downer the flow becomes inhomogeneous, and the solids velocities in the center of the downer are higher than those near the wall. This study provides a proof-of-concept design to monitor the flow dynamics in the fluidized bed by the combination of electrostatic and ECT sensors over a wide range of flow regimes. © 2013 American Chemical Society.