Hydrodynamics of cold-rig biomass gasifier using semi-dual fluidized-bed

abstract Article history:Received 21 August 2012Accepted 14 September 2012Available online 23 September 2012Keywords:GasificationSemi-dual fluidized-bed (sDFB)Solid circulation rateInternal mixingComputational fluid dynamics (CFD)Eulerian–Eulerian model This study reports a semi-dual fluidized-bed (sDFB) biomass gasifier, which is a novel design of dualfluidized-bed (DFB) with the internal mixing of solid particles between riser and gasifier to enhance theheat and mass transfer. A cold-rig experiment of sDFB (0.8 m width×0.2 m depth×3.85 m height) wasperformed to investigate fluid hydrodynamics and solid circulations. Pressures were sampled at 43 pointsalongthesDFBgasifier.Anexternalcirculation rateofsandwasmeasuredfor60 safter2 minoftheoperatingtime. In order to estimate the amount of direct back-mixing particles through the gasifier–riser interconnec-tion area, an Eulerian–Eulerian two-dimensional computational fluid dynamics (CFD) model was developedforthecold-rigsDFB.ThisCFDmodelincluded thekinetictheoryofgranularflowandthek– dispersedturbu-lence model. The CFD simulation results were validated with the experiment data. About 17% back-mixing ofparticles through the gasifier–riser interconnection area were obtained from the CFD simulation. This indi-cates that the sDFB has a possibility of having higher heat and mass transfer than the conventional DFB.© 2012 Elsevier B.V. All rights reserved.

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