Mercury distribution in fly ash components

Abstract

Six fly ash samples from different sources were studied to evaluate the mercury distribution in coal fly ash components. These samples represent three types of fly ash, i.e., Class F, Class C, and mixture of Class F and Class C. Mercury content in as-received fly ash samples varied from 9 ppb to 145 ppb. It is believed that the mercury content of fly ash is a function of the parent coal properties (e.g., bituminous or lignite, mercury content), combustion conditions, ash composition, and pollution control systems. Examination of the fly ash components (carbon concentrate, cenospheres, magnetic product, and clean ash) revealed that mercury is concentrated in the high LOI fraction of each component (up to 800 ppb). This indicates that it is associated with unburned fly ash carbon. Detailed study on three fly ash samples indicate that linear correlation exists between mercury content and LOI (loss on ignition) value of each fly ash sample. It was concluded that the unburned carbon has a high affinity for mercury and the fly ash may be ``de-mercurized`` by separating unburned carbon from fly ash.