Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Experiments were conducted in a liquid–solid circulating fluidized bed (LSCFB) of 80 mm i.d. and 2.8 m high to study the macroscopic flow structure over a wide range of liquid velocity and solids inventory in the storage vessel. The results indicate that the valve configuration (i.e. lift pot and the angle made by the solids feed pipe with the riser), solids inventory in the storage vessel and location of the primary liquid distributor were found to play an important role on the macroscopic properties of LSCFB. Dynamic leak, flow of solids from the return leg into the riser in the absence of auxiliary liquid flow, has been noticed at very high liquid velocities when the primary liquid distributor inlet (positioned at the bottom of the riser) is near to the solids feed pipe from the storage vessel. The dynamic leak was prevented by changing the position of the primary distributor inlet and the macroscopic flow behavior with and without dynamic leak was compared. The transitional liquid velocity that demarcates the conventional fluidization from the circulating fluidization was determined by three different methods and was found to be independent of solids inventory and dynamic leak.