Fluidization characteristics of power-plant fly ashes and fly ash-charcoal mixtures

A fluidization test system was designed and constructed for measurement of fluidization parameters for fly ashes and fly-ash—charcoal mixtures as part of continuing research on aluminum recovery from power plant fly ash by the HiChlor process. Bituminous and sub-bituminous coal fly ashes were tested and significant differences in fluidization characteristics were observed. Fly ashes which had been mechanically collected fluidized uniformly at low air flow-rates. Electrostatically precipitated fly ashes exhibited channeling tendencies and did not fluidize.

Fluidization characteristics of electrostatically collected ashes improved when pulverized charcoal was added. Fluidization of the mixtures was aided initially by a mechanical stirrer. Once fluidized, the mixtures would refluidize without stirring. Smooth fluidization and large bed expansion were observed. A fly-ash—coal mixture fluidized only after being oven-dried.