Regimes of large-scale fluidized beds for solid fuel conversion

• Published in: Powder technology Vol. 308; pp. 362 - 367
• Main Author: Leckner, Bo
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-02-2017; Elsevier BV
• Subjects: Boiler; Boiler furnaces; Boilers; Bubbling; Circulating fluidized bed; Clustering; Converters; Dilution; Fluid dynamics; Fluid flow; Fluidization; Fluidization regime; Fluidized bed boilers; Fluidized beds; Furnaces; Gasification; Gasifier; Group dynamics; Particulates; Solid fuel; Solid fuels; Temperature; Terminal velocity; Turbulence; Velocity; Fluidization regime; Circulating fluidized bed; Boiler; Solid fuel; Gasifier
• ISSN: 0032-5910; 1873-328X; 1873-328X
• DOI: 10.1016/j.powtec.2016.11.070

The description of the fluidization behavior of Group B particles is ambiguous at high velocities in wide vessels like those in commercial solid-fuel converters, such as boiler furnaces and gasifiers. Bubbling, turbulent, and fast-fluidization regimes are analyzed here, especially related to fuel converters. It is claimed that the bottom bed in fluidized-bed boilers is operated in a bubbling regime of fluidization even at high gas velocities accompanied by a tall splash zone, as long as there is sufficient bed material in the system. It is also shown that the upper part of conventional circulating fluidized-bed boilers operates in a dilute-flow mode. In denser flows, a comparison between transport velocity and terminal velocity indicates that clustering flow is much stronger for Group A particles than for Group B, and hence, fast fluidization should be less developed for Group B than for Group A particles. The influence of temperature is also shown.
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•Fluidization regimes in reactors for solid fuel conversion are studied.•They have a “bubbling” bottom bed, a splash zone, and a disperse-flow in the riser.•In contrast, most publications relate to turbulent and fast fluidization.