Energy & Fuels · 2006 · 145 citations · 14 references
Natural SciencesChemistryEnvironmental SciencesAir PollutionCombustionEnvironmental ChemistryAerosol ChemistryAerosol ScienceAir Pollution MeasurementCombustion AnalysisParticulate MatterSecondary Aerosol FormationAerosol CharacterizationAerosol Composition EffectsAerosol PropertiesCarbon DioxideFine Particle FormationGeometric Mean DiameterMercury Speciation AnalysisVaporization
The study compared submicrometer ash and mercury speciation in coal combustion under O₂–CO₂ versus conventional air. Experiments varied O₂:CO₂ and O₂:N₂:CO₂ ratios. Replacing nitrogen with CO₂ reduced submicrometer ash mass and size by ~28 %, while higher O₂:CO₂ or N₂:CO₂ ratios increased particle size due to faster vaporization; primary particles were spherical and the elemental‑to‑oxidized mercury ratio remained ~4:1 in both combustion modes.
The characteristics of the submicrometer mode of ash and mercury speciation on combustion of coal in an oxygen−carbon dioxide and air (conventional) system were compared. The experiments were conducted at different O2:CO2 and O2:N2:CO2 mixing ratios. On replacing the nitrogen in air with carbon dioxide, the total mass of the particles in the submicrometer mode (<0.5 μm) of ash was smaller. Correspondingly, the geometric mean size (dpg) of the submicrometer aerosol was smaller by approximately 28%. When the O2:CO2 ratio was increased from 1:4 to 4:4, the geometric mean size of the submicrometer mode increased from 29 to 54 nm because of a faster vaporization rate as a result of a higher coal particle temperature. An increase in the geometric mean size was observed on increasing the N2:CO2 ratio at a fixed O2 concentration because of the same reasons. The shape of the primary particles was spherical in all the tests, indicating that a vapor to particle transformation pathway was prevalent. The ratios of elemental to oxidized mercury (approximately 4:1) were similar for O2−CO2 and air combustion.
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