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Dynamics of fines deposition in an alternating semifluidized bed



A semifluidized bed was proposed to allay bed plugging during the filtration of fines-hydrocarbon suspensions. Mitigation of plugging was allowed by alternating semifluidization during capture with unconstrained fluidization for removal of deposits. Solids holdup conditions were established to prevent deposition in the fluidization section. The cyclic parameters were varied to allow efficient removal of deposits during washing. Analysis with a filtration model accounting for solids detachment in the fixed bed section revealed that the fluidization section favored growth of aggregate size entering the fixed bed. Analysis of the split ratios between fixed and fluidized bed heights revealed that the shallowest fluidization sections delayed deposition in the fixed bed. In cyclic operation, reversibility of the semifluidized bed was best recovered via gas injection during the washing stages. However, the filtration times in successive cycles shortened with increasing washing times but lengthened with increasing the washing superficial suspension velocity. © 2008 American Institute of Chemical Engineers AIChE J, 2008