Jk. Lee et Sc. Kim, Electrostatic beneficiation of coal fly ash utilizing triboelectric charging with subsequent electrostatic separation, KSME INT J, 15(6), 2001, pp. 804-812
triboelectrostatic separation system for removing unburned carbon from coal
fly ash is designed and evaluated. Fly ash from a coal-fired power plant i
s used as an accepted additive in concrete where it adds strength, sulfate
resistance and reduced cost, provided acceptable levels of unburned carbon
are maintained. Unfortunately, unburned carbon in coal fly ash absorbs some
of other additives and reduces the concrete strength. This paper describes
to investigate dry triboelectrostatic process to separate unburned carbon
from coal fly ash and utilize it into economically valuable products. The l
aboratory-scale triboelectrostatic separation system consists of a particle
feeding system, a tribocharger, a separation chamber, and collection syste
ms. Particles of unburned carbon and fly ash can be imparted positive and n
egative surface charges, respectively, with a copper tribocharger due to di
fferences in the work function values of the particles and the tribocharger
, and can be separated by passing them through an external electric field.
Results showed that fly ash recovery was strongly dependent on the electric
field strength and the particle size. 70 wt% of fly ash containing 6.5 wt%
of carbon contents could be recovered at carbon contents below 3%. The tri
boelectrostatic separation system showed a potential to be an effective met
hod for removing unburned carbon from coal fly ash.