REMOVAL OF UNBURNED CARBON FROM COAL FLY ASH USING A PNEUMATIC TRIBOELECTROSTATIC SEPARATOR

Abstract

A pneumatic triboelectrostatic beneficiation system of fly ash was studied using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests were conducted to evaluate the charge density and the separation efficiency at various operating conditions. It was found that the higher charge densities were obtained at [1] the air flow rate of 1.75 m³/min, [2] the feed rate of less than 50 kg/h, and [3] the relative humidity of less than 30% with use of a stainless ejector tribocharger. With these optimum conditions, the clean ash of less than LOI 3% was recovered with a yield over 75% when operated at the diffuser slit gap of 4 mm, the diffuser outlet velocity of 16.1–18.6 m/s, and the distance of 15 cm between diffuser slit and splitter. The optimum feed rate was found to be 740 kg/h per m² of electrode surface area, which can be used as a scale-up factor of electroseparator.

Keywords:

• Fly ash
• Unburned carbon
• Electrostatic separation
• Tribocharging
• Faraday cage

Acknowledgments