Influence of bulk solids cross-flow on lateral mixing of fuel in dual fluidized beds

• In typical dual fluidized bed systems — used e.g. in chemical looping combustion or indirect gasification ofbiomass for production of second-generation biofuels — the bulk solids are continuously circulating between atall 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 bymeans of mathematical modeling and to investigate the effect of the cross-flow of bulk solids on the lateralmixing of fuel particles.Experiments relevant for industrial conditions are carried out in a fluid dynamically downscaled cold flowmodelof an existing indirect gasifier. It is found that the velocity field of the bulk solids induced by the solids cross-flowcan be described by a potential function obtained from a diffusion equation. As for the fuel particles, their sliprespect to the bulk solids cross-flowis quantified using a cross-flowimpact factor, θ, which is found to be a linearfunction of fluidization velocity and in the range 0.18–0.68 for the conditions investigated. Finally, we concludethat the fuel mixing in fluidized beds with a significant cross-flow of bed material can be described by aconvection–diffusion equation.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Keyword

Lateral mixing

Cross-flow

Fluidized bed

Publication and Content Type

art (subject category)

ref (subject category)