Experimental and analytical study of the solids circulation loop of a compartmented fluidized bed

Experiments were conducted to identify the necessary conditions for achieving stable operation and identify the operational range of a novel fluidized solids circulation system using a compartmented fluidized bed and vertical transport line (VTL). The VTL has allowed the conveying of relatively fine particles (Group B - near the transition from Group A to B) under a wide range of experimental conditions. It was also demonstrated that the nozzle geometric configuration can alter the entrainment behaviour of the motive gas jet quite significantly by altering the flow patterns in the vicinity of the jet. Of all the geometric modifications studied, the inclined plate and the shroud were shown to have the most favourable impact on the entrainment rate. A CO2 tracer study quantified the amount of fluidization gas entrained into the VTL riser for the closed loop configuration. It was discovered that a significant amount of gas leaked back out into the fluidized bed from the motive gas jet. An empirical model was derived in order to further characterize the system behaviour. For fully developed flow, the main resistive forces in the riser for a given solids holdup were the solids weight and solids-wall friction, however, the pressure drop from the nozzle tip to the riser inlet is significant and affects the solids flow rate and pattern. Specifically, it was shown that the solids entrainment into the riser is highly dependent upon the system pressure balance when comparing a solids circulation loop with an open configuration to one that was closed. (c) 2007 Elsevier B.V. All rights reserved.