Basic research on enhancing decarburization of micro-fine fly ash by nanobubbles (NBs) flotation

The mineralization efficiency of micro-fine unburned carbon particles in flotation process is low due to the fine particle size of fly ash and the large volume and relatively small surface area of conventional bubbles, which increased the difficulty of decarbonizing fly ash. The effect of NBs flotation on micro-fine fly ash was studied by flotation test, contact Angle analysis and Zeta potential analysis. The results show that compared with the conventional flotation technology, NBs flotation shows a better carbon removal effect, effectively saves flotation reagents dosage, even better decarburization index under the condition of low aeration or high pulp density. In addition, NBs flotation completed the decarburization of fine fly ash 60s earlier than conventional flotation, which improved the decarburization rate of fly ash. The mechanism study found that the presence of NBs can reduce the surface potential of unburned carbon and enhance the surface hydrophobicity of unburned carbon, reduce electrostatic repulsion between unburned carbon particles and increase the hydrophobic attraction, which ensure unburned carbon particles maintain a stable hydrophobic aggregate structure to significantly improve the adhesion probability of conventional bubble-particles.