Separation of unburned carbon from coal fly ash: A review

Coal fly ash, the main industrial waste in coal-fired power plants generated during the coal combustion, usually re-utilized as raw materials in construction industry. However, a lot of unburned carbons are contained in raw fly ash, which not only decreasing the strength of fly ash concrete but also causing a huge waste of the resources. Separation of unburned carbon from fly ash is an efficient way to achieve a higher efficiency in the utilization of waste fly ash and greater economic and environmental benefits. This review highlights current methods for separating unburned carbon from fly ash, such as sieving, gravity separation, electrostatic separation, froth flotation, and oil agglomeration. The mineralogy features of unburned carbon affecting the separation efficiency are also presented. This review is closed with a brief discussion on the future research directions addressing different problems related to the recovery of unburned carbon. (C) 2019 Elsevier B.V. All rights reserved.