An Alternative to Additional So₃ Injection for Fly Ash Conditioning


Small concentrations, approximately 2-10 parts per million (ppm), of injected sulfur trioxide (SO3) have improved particulate collection efficiencies of electrostatic precipita-tors burning lower-sulfur coal. However, the addition of extra SO3 not only incurs costs but also presents negative environmental effects. This work explored a method that could be applied to existing coal-fired power plants to convert the sulfur dioxide (SO2) already present in the flue gas to sufficient levels of SO3 for fly ash conditioning as an alternative to adding SO3 by burning elemental sulfur. During this research, a pre-mixed natural gas flame was used to promote the conversion of SO2 to SO3 in a drop-tube furnace with average non-flame, free stream gas temperatures of 450 and 1000 K. SO3 concentrations measured by wet chemistry and confirmed using elemental balances of other sulfur species measured by gas chromatography revealed that as much as 7% of SO2 was homogeneously transformed to SO3. The results also showed that at low temperatures, the rate at which SO3 is converted back to SO2 decreased, thus extending the time period during which SO3 concentrations would be sufficient for ash conditioning. An additional benefit of this technique is speculated to result from increased flue gas humidity.


Mechanical and Aerospace Engineering

Keywords and Phrases

Carbon; Coal; Sulfate; Coal; Natural Gas; Sulfur Derivative; Sulfur Dioxide; Sulfur Trioxide; Unclassified Drug; Air Pollutant; Air Pollution; Article; Chemistry; Fly Ash; Industrial Waste; Particulate Matter; Acid Rain; Chemical Reaction; Combustion; Electric Power Plant; Electrostatic Precipitation; Flue Gas; Fly Ash; Furnace; Gas Chromatography; Humidity; Priority Journal; Temperature; Air Pollutants; Occupational; Air Pollution; Carbon; Coal; Industrial Waste; Particulate Matter; Sulfates

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


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© 2000 Air and Waste Management Association, All rights reserved.

Publication Date

01 Feb 2000