Species and thermal stability of mercury captured by fly ashes

Abstract

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 Cl content in coal does not absolutely result in the capture of more mercury by ash, but can result in high HgCl2 ratio in particulate mercury. The HgO ratios are low, and the HgSO4 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. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 460–467, 2017

Impact of Nonoxidized Sulfur Species on Elemental Mercury Removal by SO2 Activated Petroleum Cokes

“…As shown in Figure , the desorption peaks which indicated different adsorbed mercury forms in SO 2 -activated cokes can be expected to be the same. Concerning the desorption characteristics of the reference mercury compounds reported in previous studies, it can be deduced that mercury was mainly bound to nonoxidized sulfur species in the forms of HgS black and HgS red, and the rest peaks can be assigned to mercury bound to organic carbon matter (Hg–OM), HgO, mercury bound to organic sulfur matter (Hg–SR), Hg 2 SO 4 , and HgSO 4 , respectively. − Furthermore, distinct differences in mercury species distribution between samples derived from different sulfurization methods were observed. As can be seen from Figure , heat treatment in N 2 enabled the highest desorption peak shifting from HgS red to HgS black, resulting in weaker thermal stability with the percentage of adsorbed mercury decomposed at 200–300 °C increased from 15.18% in PC-S to 23.49% in PC-NS.…”