UBC Theses and Dissertations
A novel circulating fluidized bed Fusey, Isabelle
A novel type of circulating fluidized bed has been investigated and tested. While a conventional circulating fluidized bed unit consists of two vessels standing side by side - a fast bed operating at high gas velocity, and a slow bed which acts as a recycle vessel and operates at a much lower velocity - the novel design incorporates the two beds into a unique concentric arrangement. The inner column acts as the fast bed and the annular region acts as the slow bed. A baffle to separate the gas-solid mixture at the top of the inner column has been designed and tested. The baffle works reasonably well but design optimization is needed. Two types of air inlets for aeration of the insert have been tried: vertical and tangential. The vertical air inlet has been found to produce the highest solids circulation rates. Two types of solids have been investigated: polyvinyl chloride resin and cracking catalyst. The use of the heavier and smaller cracking catalyst particles resulted in higher circulation rates and greater solids hold-up in the inner column. The hydrodynamic behavior of the system has been studied using pressure and circulation flux measurements. The solids circulation flux, the axial pressure profile, and the absolute pressure inside the system are generally all strong functions of air velocity in both the inner and outer sections, solids inventory, type of particle, and type of air inlet.
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