Tests were conducted to investigate the triboelectrostatic processfor separating unburned carbon from coal fly ash. Using a batch typeseparator composed of two parallel plates and anejector-tribocharger, the charge density and the separationefficiency were evaluated under various operating conditions. Theseincluded the air flow rate, the solids loading, the relative humidityand the temperature of the air, and the voltage between the towparallel electrodes. It was found that the relative humidity of thesurrounding air was the most influencing factor of the charge densityas well as the separation efficiency. The maximum charge density wasobtained at the air flow rate of 326 e/min, and the air temperatureof 74 deg C when operated at solids loadings less than 290 g/m~3 andat lower than 30/100 relative humidity. At the optimum conditions, afly ash of 7.5/100 LOI could be processed into a 3.0/100 LOI productwith a recovery over 80/100.
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