Electrostatic beneficiation of fly ash using an ejector‐tribocharger

Abstract

Tests were conducted to investigate the triboelectrostatic process for separating unburned carbon from coal fly ash. Using a batch type separator composed of two parallel plates and an ejector‐tribocharger, the charge density and the separation efficiency were evaluated under various operating conditions. These included the air flow rate, the solids loading, the relative humidity and the temperature of the air, and the voltage between the two parallel electrodes. It was found that the relative humidity of the surrounding air was the most influencing factor of the charge density as well as the separation efficiency. The maximum charge density was obtained at the air flow rate of 326 l/min, and the air temperature of 74 °C when operated at solids loadings less than 290 g/m3 and at lower than 30% relative humidity. At the optimum conditions, a fly ash of 7.5% LOI could be processed into a 3.0% LOI product with a recovery over 80%.