Ab initio calculations were performed to study the quantum chemistry reactions mechanisms among Hg(0), elemental halogen and O3. The geometry of reactions, transition states (TS), intermediates (M) and products were optimized using the MP2 method at the SDD basis function level for Hg, and using 6-311++G (3df, 3pd) for other species. Molecular energies were calculated at QCISD (T) level with zero point energy. Activation energies were calculated along with pre-exponential factors . The reaction rate constants within 298-1800 K were calculated according to transition state theory (TST). The influences of O3 on the reaction of Hg(0) with halogen are discussed. Hg(0) can be oxidized to Hg(1+) by halogen and O3, and halogen and O3 can be arranged in decreasing order as: Br2 > BrO > O3 > Br > Cl, BrCl > HBr > HCl, Br2 > Cl2 according to reaction rate constants. When O3 is presented, Br2, HBr, BrCl, Cl2 and HCl react with O3 and are initially converted to BrO and ClO. O3 is unfavorable for oxidation of Hg(0) by Br2. The mixture of HBr and O3 has better oxidizing Hg(0) performance than HBr and O3. Cl is less effective than Br for oxidation of Hg(0).

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

In order to study the effect of additives on mercury speciation in coal‐fired derived flue gases, the additives experiment was conducted in one 110MW coal‐fired power plant, the additives including calcium bromide and iron oxide. Taking advantage of the Ontario Water Act (OHM) and sorbent tube method, mercury at the denitration (SCR) entrance and export and desulfurization (WFGD) entrance was sampled and the variation of mercury before and during adding the additives was analyzed. The results show that the additives of calcium bromide can oxidize elemental mercury and contribute to increasing the proportion of divalent mercury, and in denitration device, the ratio of divalent mercury in flue gas shows an increasing trend along with the increasing of calcium bromide. However, there is no such trend appearing at desulfurization entrance. In addition, the additives of iron oxide have no obvious effect on the oxidation of elemental mercury in flue gas. Adding a small amount of iron oxide has little effect on the form of mercury, and may even reduce the proportion of divalent mercury. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1566–1574, 2016