Effect of Internals on the Hydrodynamics of Circulating Fluidized Bed Reactors

摘要

Non-uniformity in the radial solids hold-up is characteristic of circulating fluidized bed (CFB) with a high concentration of solids flowing mainly downward near the wall and most of the gas passing through the central core region. As a result, gas solids contact is poor in the riser although much better than bubbling bed. In this study, the effect of ring-type internals on the reduction of non-uniformity in the riser of 7.6 cm in diameter and 3 m in height was investigated. Two ring internals with opening areas of 70% and 90% were installed in five axial positions in the riser. Measurement results of solids hold-up distribution of sand particles obtained by using fibre optic probe indicate that the internals reduce radial non-uniformity. It was also observed under high superficial gas velocity and low solids circulation rate, one can have reversed radial solids distribution profile: more dilute in the wall region than in the core region. Detailed study on the radial solids distribution around ring internals show the formation of a denser region above the 70% opening ring than above the 90% opening one and a more dilute region below the both rings.