The role of electrical heating on tribocharging and triboelectrostatic beneficiation of fly ash

Triboelectrostatic beneficiation is an effective technique to remove unburned carbon from fly ash. The purpose of this study is to enhance the particles tribocharging, and improve the efficiency of removal unburned carbon from fly ash using electrical heating. An experimental system with electrical heating was established to realize the tribocharging measurement and fly ash triboelectrostatic beneficiation. The experimental material collected from a thermal power station was fly ash with an average loss on ignition of 20.76%. The operating conditions were electric field voltage of 40KV and air flow rate ranging from 1.7 to 4.25 m/s. The influence of heating temperature and heating position on tribocharging and triboelectrostatic beneficiation was discussed. The feasibility of electrical heating was evaluated by the charge-to-mass ratio (CMR), loss on ignition (LOI) and removal unburnt carbon rate (RCR). The results indicate that the increasing of collision probability for heated particles can improve the charging efficiency. The heating temperature related to gas moisture content and particles dielectric constant is inversely proportional to the LOI of ash, whereas it is opposite for the RCR. The heating position has an effect on the CMR and RCR because of changed contact time between charged particles and compressed air. The optimum conditions are the air flow rate of 4.25 m/s, heating temperature of 90℃. Heating tube III is suitable to install electrical heating system. The electrical heating is proved to be effective to improve the efficiency of fly ash triboelectrostatic beneficiation.