Particle collision during the tribo-electrostatic beneficiation of fly ash based on infrared thermography
HS Li, YH Chen, KB Wu, XX Zhang
Tribo-electrostatic beneficiation is effective for separating unburned
carbon from fly ash. During the process, the fly ash particles become
charged owing to friction and collision inside a tribo device. The
intensity of friction and collision between particles can be deduced
from the tribo device temperature field, obtained by infrared
thermography. The purpose of this research was to establish whether
an appropriate configuration of tribo device models can be obtained
from particle collision experiments using infrared thermography. An
experimental set-up was configured to study tribo devices with
different arrangements and spacing of the friction rods, and the effect
that this has on interparticle collision and the tribo-electrostatic
beneficiation process. The experimental material was fly ash particles
with a size range from 38 µm to 74 µm and loss on ignition (LOI)
12.65%. The operating conditions were electric field voltage 40 kV
and the air flux ranged from 12 to 24 m3/h. The results show that the
temperature inside the tribo devices is directly proportional to air flux
and particle collision rate. The arrangement and spacing of the
friction rods has an important effect on the temperature field distribution.
An equilateral triangular arrangement with 20 mm spacing
significantly increases the temperature value and collision
probability. The optimum operating parameters were established
through tribo-electrostatic beneficiation experiments on the fly ash,
and the results (LOI of the product at the two electrodes and rate of
removal of unburned carbon at the negative plate) were consistent
with those of the infrared thermography experiments. A tribo device
with friction rods configured in an equilateral triangle arrangement
and with 20 mm spacing again yielded the best results. This approach
constitutes a new technique for the optimization of tribo device
design.
Keywords: fly ash, tribo-electrostatic beneficiation, tribo device, infrared
thermography.