Flotation separation of unburned carbon from coal fly ash using a flotation column

A fly ash sample from a power station in Guangdong province has been characterized by size separation, X-ray diffraction, contact angle measurements and X-ray Fluorescence. The ash sample had a loss-on-ignition (LOI) (%) of 15.54% and a large proportion of the unburned carbon was distributed in the +74 µm and -20 µm fractions. Contact angle measurements suggested that the removal of unburned carbon from the fly ash using flotation would present some challenges. The effects of various operating variables on the removal rate of unburned carbon (RUC) (%) and (LOI) (%) were determined using a cyclonic-static micro bubble flotation column (FCSMC). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil (frother) dosage was 600 g/t, pulp density was 20%, superficial gas velocity was 1.4 cm/s and circulating pressure was 0.20Mpa. Column flotation tests indicated that the FCSMC method a viable and effective separation process for removing the unburned carbon from the fly ash. Under the optimized conditions, a clean ash with 2.13% LOI and 94.21% RUC was obtained.