Particle Collision during the tribo-electrostatic beneficiation of fly ash based on infrared thermography

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 mu m to 74 mu m 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 m(3)/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.