COCURRENT DOWNFLOW CIRCULATING FLUIDIZED-BED (DOWNER) REACTORS - A STATE-OF-THE-ART REVIEW

In the last decade, cocurrent downflow circulating fluidized bed react ors, called ''downer'' reactors, have been proposed as an alternative to upflow circulating fluidized bed, or ''riser'', reactors. In this p aper, published results on downer studies are summarized and future di rections of research are recommended. Downer reactors are shown to hav e several distinct advantages over upflow circulating fluidized bed re actors and can potentially be used in many industrial processes, mainl y due to a more uniform gas and solids flow structure compared with ri sers.