Influence of bulk solids cross-flow on lateral mixing of fuel in dual fluidized beds
Artikel i vetenskaplig tidskrift, 2015

In typical dual fluidized bed systems — used e.g. in chemical looping combustion or indirect gasification of biomass for production of second-generation biofuels — the bulk solids are continuously circulating between a tall high-velocity riser and a bubbling bed. This circulation results in a solids cross-flow in the bubbling bed,which creates a net convective solids flow. The aims of this paper are to describe this convective flow by means of mathematical modeling and to investigate the effect of the cross-flow of bulk solids on the lateral mixing of fuel particles. Experiments relevant for industrial conditions are carried out in a fluid dynamically downscaled cold flowmodel of an existing indirect gasifier. It is found that the velocity field of the bulk solids induced by the solids cross-flow can be described by a potential function obtained from a diffusion equation. As for the fuel particles, their slip respect to the bulk solids cross-flowis quantified using a cross-flowimpact factor, θ, which is found to be a linear function of fluidization velocity and in the range 0.18–0.68 for the conditions investigated. Finally, we conclude that the fuel mixing in fluidized beds with a significant cross-flow of bed material can be described by a convection–diffusion equation.

Lateral mixing


Fluidized bed


Erik Sette

Chalmers, Energi och miljö, Energiteknik

David Pallarès

Chalmers, Energi och miljö, Energiteknik

Filip Johnsson

Chalmers, Energi och miljö, Energiteknik

Fuel Processing Technology

0378-3820 (ISSN)

Vol. 140 245-251