The Recovery of Unburned Carbon from Coal Bottom Ash Using Froth Flotation: The Taguchi Optimization Method

The high consumption of coal in thermal power plants generates a significant amount of bottom ash, most of which is currently disposed of in landfills. However, the presence of unburned carbon in bottom ash limits its potential applications. To enable its use in construction materials, it is essential to reduce the unburned carbon content. Flotation is a promising technique for removing or recovering unburned carbon due to its high throughput and efficiency. This study aimed to optimize key parameters in the flotation process for recovering unburned carbon from bottom ash. The target was to achieve a tailing loss on ignition (LOI) of less than 6%, in accordance with ASTM C618 standards for concrete applications. The parameters evaluated in this study included the frother dosage, collector dosage, air flow rate, and pH. Optimization was conducted using the Taguchi method, which identified frother dosage as the most influential factor in flotation recovery, contributing 80.55%. Additionally, the air flow rate was found to have the greatest impact on combustible recovery (73.34%) and carbon content in the concentrate (41.05%). The optimized process resulted in a tailing LOI of 5.3%, meeting ASTM C618 requirements. These findings demonstrate the effectiveness of the Taguchi method in optimizing the flotation process for bottom ash treatment.