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Computational modelling of the impact of particle size to the heat transfer coefficient between biomass particles and a fluidised bed

By K. Papadikis, S. Gu and A.V. Bridgwater

Abstract

The fluid–particle interaction and the impact of different heat transfer conditions on pyrolysis of biomass<br/>inside a 150 g/h fluidised bed reactor are modelled. Two different size biomass particles (350 ?m and 550 ?m<br/>in diameter) are injected into the fluidised bed. The different biomass particle sizes result in different heat<br/>transfer conditions. This is due to the fact that the 350 ?m diameter particle is smaller than the sand particles<br/>of the reactor (440 ?m), while the 550 ?m one is larger. The bed-to-particle heat transfer for both cases is<br/>calculated according to the literature. Conductive heat transfer is assumed for the larger biomass particle<br/>(550 ?m) inside the bed, while biomass–sand contacts for the smaller biomass particle (350 ?m) were<br/>considered unimportant. The Eulerian approach is used to model the bubbling behaviour of the sand, which<br/>is treated as a continuum. Biomass reaction kinetics is modelled according to the literature using a two-stage,<br/>semi-global model which takes into account secondary reactions. The particle motion inside the reactor is<br/>computed using drag laws, dependent on the local volume fraction of each phase. FLUENT 6.2 has been used<br/>as the modelling framework of the simulations with the whole pyrolysis model incorporated in the form of<br/>User Defined Function (UDF)

Topics: T1
Year: 2010
OAI identifier: oai:eprints.soton.ac.uk:147401
Provided by: e-Prints Soton
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