Field tests on mercury speciation and emission while burning Kentucky and Illinois coals with different chlorine contents were performed in a 100-MWe pulverized-coal boiler with low-NO x burners. Seven coals were used during the tests and were grouped into two sets for comparison, with the baseline coal being shared between the two sets. The first set of four coals was used to investigate the effect of chlorine in coal on mercury emission and its speciation by selecting coals with similar mercury contents and different chlorine contents. The four coals in the second set were selected to investigate the effect of mercury contents in coal on mercury emission and its speciation by choosing coals with similar chlorine contents and different mercury contents. The mercury concentration and speciation in the flue gas were determined using the American Society for Testing and Materials (ASTM) standard Ontario Hydro Method (OHM) and a PS Analytical Semi-continuous Emissions Monitoring (SCEM) system. Flue gas samplings were performed at two locations:  upstream before the electrostatic precipitator (ESP) inlet and downstream after the ESP outlet. A thorough comparison between the two monitoring methods was made. A sampling bias was found in the OHM sampling performed at the ESP inlet, because of the accumulation of ash with a high carbon content on the OHM filter. An ash-free sampling probe should be used with the OHM impinger train for obtaining accurate mercury information whenever ash concentrations are high. Mercury emission and speciation for the seven test coals at the ESP outlet location are described and discussed. Results indicate that the coal chlorine content has an impact on the mercury oxidation processes, which are mitigated by high concentrations of SO2. It is speculated that SO2 limits Cl2 formation.

The Western Kentucky University mobile laboratory for monitoring mercury emissions measured the mercury levels in a 100-MW boiler with wall-fired low-NO x burners. Mercury emissions were monitored while burning seven coals, using semicontinuous emission monitoring at the air preheater outlet and electrostatic precipitator outlet. The collected data was then scaled and analyzed using stepwise regression analysis. The results showed that initial mercury concentration in the coal, as well as chlorine and sulfur levels, all influence the amount of mercury emissions. After mercury content, chlorine had the major role in the levels of vapor-phase mercury present in the flue gas. Chlorine promotes the chemisorption of mercury onto fly ash. Sulfur was shown to be a major factor in the oxidation of elemental mercury but inhibited the adsorption of oxidized mercury onto the fly ash. Further experimental results suggest that both HCl and SO2 may participate directly in the mercury oxidation mechanism.

Eight commercial fly ash samples including two from petroleum coke/coal co-firing were characterized to determine the origin, structure, and properties of the unburned carbon. Because of its relevance to ash utilization, the characterization included measurements of adsorptivity toward concrete surfactants, and its dependence on carbon form, particle size, and contact time. The coal/coke co-firing ashes are observed to possess unique optical and adsorptive properties which are related to the size, density, and internal porosity of the coke-derived residual char.