Species and Thermal Stability of Mercury Captured by Fly Ashes

摘要

Samples of fly ash were obtained from four boilers in China. The unburned carbon content, mercury concentrations, and mean ash particle size were measured. The ashes were heated at seven different temperatures, and the mercury released from the heated ashes was determined. The mercury species in the ashes were analyzed. The correlation between the mercury captured by ash and the carbon in ash was determined. The ratio of Hg to ash has an important role in particulate Hg formation. The high CI content in coal does not absolutely result in the capture of more mercury by ash, but can result in high HgCl_2 ratio in particulate mercury. The HgO ratios are low, and the HgS0_4 ratios of all the ashes are negligible. The sulfur in coal is an important factor in the sorption of mercury by fly ash, and the high S content in coal results in a high HgS ratio in ash.