Bottom-bed fluid dynamics – Influence on solids entrainment
Journal article, 2018

In CFB boilers, the solids concentration along the riser and the external solids circulation are important design parameters. This work provides an experimental investigation on how the solids entrainment from the bottom region of a CFB riser is influenced by the fluidization conditions, in particular if there is a bottom bed or not. Measurements are carried out in a CFB riser with a height of 3 m and 0.45 m 2 in cross section. The solids inventory consists of glass spheres with a mean size of 112 μm, employing fluidization velocities up to 1.4 m/s and riser pressure drops in the range 0.15–1.5 kPa. The vertical distribution of solids concentration is determined through pressure drop measurements along the riser height. The external solids circulation is measured with a valve system in the return leg. The results show that the bottom region conditions govern how operational parameters influence the characteristics of the solids entrainment from the bottom. The vertical extension of the splash zone above the dense bed depends strongly on the dense bed height. In the absence of a dense bed, a bottom region with strong solids back-mixing is established which has similarities with the splash region.

Solids entrainment

Dense bottom bed

Circulating fluidized bed (CFB)

Solids circulation


Tove Djerf

Chalmers, Space, Earth and Environment, Energy Technology

David Pallarès

Chalmers, Space, Earth and Environment, Energy Technology

Filip Johnsson

Chalmers, Space, Earth and Environment, Energy Technology

Fuel Processing Technology

0378-3820 (ISSN)

Vol. 173 112-118

Subject Categories

Energy Engineering

Geotechnical Engineering

Ocean and River Engineering



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