Scanning Electron Microscopy


Sodium sesquicarbonate (NaHCO3-Na2CO3-2H2O) and the mineral trona (NaHCO3-Na2CO3-2H2O) have been utilized as effective dry sorbents for SO2 in flue gas during fossil fuel plant full-scale injection studies conducted at the Cameo Station, Unit 1, of Public Service Company of Colorado near Grand Junction, CO. Microstructural and microchemical characterization studies of fly ash samples from these studies identify decomposition features for these carbonates that relate to the development of satisfactory reaction surface areas for combination with SO2 from flue gas. The major features are non-sulfur bearing microspheres and a mixture of fly ash and the sulfur bearing carbonate reaction products. Evidence is presented to confirm a thermal decomposition model in which particle breakup or rubbling occurs (the so-called popcorn effect) due to the build-up of carbonate decomposition gases (CO2 and water vapor) within the carbonate. These correlate with bench top laboratory studies reported earlier.

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