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Density functional theory has been employed for the modeling of activated carbon (AC) using a fused‐benzene ring cluster approach. Oxygen functional groups have been investigated for their promotion of effective elemental mercury binding on AC surface sites. Lactone and carbonyl functional groups yield the highest mercury binding energies. Further, the addition of halogen atoms has been considered to the modeled surface, and has been found to increase the AC's mercury adsorption capacity. The mercury binding energies increase with the addition of the following halogen atoms, F > Cl > Br > I, with the fluorine addition being the most promising halogen for increasing mercury adsorption. © 2006 American Institute of Chemical Engineers Environ Prog, 2006

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Part 1 (10.1021/acs.energyfuels.6b00420) of this two part series presented a computational study of NO x formation during methane and ethylene combustion, representative of small fuel fragments present in natural gas and chemical processing. The influence of fuel chemistry, reaction temperature history, and inert dilution was examined using popular models present in the literature. The present work extends the study to hydrogen-rich conditions to remove the fuel variability dependency of NO x and identify possible inconsistencies in predicting NO x during high hydrogen content fuel combustion. A comprehensive chemical kinetic model is proposed consisting of CO/H2/NO x oxidation with the full implementation of thermal, N2O, and NNH paths of NO x evolution. Predictions from the model are compared against multiple experimental data sets over a wide range of venues and operating conditions. The experimental venues include shock tube, plug flow reactor, and stirred reactor experiments that cover pressures from 1 to 100 bar and equivalence ratios from 0.5 to 1.5. In general, the overall model predictions are in good agreement with global combustion targets, such as ignition delay time, as well as with more detailed measurements from flow reactors and stirred reactors. Simulations are conducted for a wide range of reacting mixtures (H2/O2/N2, CO/H2/O2, and CO/H2O/O2/N2) with initial NO and NO2 perturbations to consider exhaust gas recirculation (EGR) conditions.

This paper describes a detailed reaction mechanism for Br/Hg/Cl chemistry in coal-derived flue gas and interprets the Hg oxidation performance across a broad range of Br addition rates in recent field tests at plants Miller, Milton R. Young, and Monticello that burn low-rank coals. The dominant channels of the homogeneous Hg chemistry with Br are analogous to those for Cl, whereby a Br atom partially oxidizes Hg 0 into HgBr, which is then oxidized into HgBr 2 by Br 2 . Mercury also oxidizes heterogeneously on unburned carbon (UBC) with Br species. This mechanism is analogous to the surface mechanism for Cl species, except that (i) elemental mercury (Hg 0 ) adsorption is faster on brominated sites and (ii) the higher Br atom concentrations in flue gas promote recombination reactions that maintain very low surface coverages of Hg/Br species. Therefore, the accelerated Hg 0 adsorption rate on brominated UBC promotes Hg 0 oxidation at the hottest gas cleaning temperatures but does not enhance the production of particulate Hg (HgP). The amount of HgP was predicted to increase for progressively greater loss-on-ignition (LOI) levels, although the removals of this form of Hg by electrostatic precipitators (ESPs) are always low for low-rank coals.