Fuel, Vol.242, 174-183, 2019
Effect of the intensification of preconditioning on the separation of unburned carbon from coal fly ash
Coal fly ash is the main by-product in coal combustion power stations. Unburned carbon in coal fly ash indicates energy waste and acts as a potential obstacle to the utilization of coal fly ash. The purpose of the study involves examining the flotation intensification for the separation of unburned carbon from coal fly ash in the presence of preconditioning. Pulp conditioning before flotation using a stirred tank ensuring that the flotation process is effective to the maximum possible extent. In this paper, prospective conditioning-flotation tests were conducted to study the process intensification for the froth flotation of coal fly ash. The interaction behavior of preconditioning on the separation of unburned carbon was investigated by conducing flotation tests. Six flotation kinetic models were used to fit the flotation kinetic test data of cumulative unburned carbon recovery under different conditioning speeds by using the 1stOpt statistical analysis software, and the results indicated that the model 2 of first-order model with rectangular distribution was most reasonable for the data fitted of coal fly ash flotation with preconditioning. Additionally, the microstructure and element composition of concentrates and tailings ash were presented by SEM-EDS and XPS analysis, and indicated that the separation efficiency of unburned carbon from coal fly ash could be improved significantly by the process intensification. The flotation intensification mechanism of preconditioning was discussed based on the surface hydrophobicity and floatability of coal fly ash particles. The contact angle increased with increases in the conditioning speed, while the induction time decreased, and there were significant differences in the state of bubble-particle attachment.