Open AccessSeparation of flue-gas scrubber sludge into marketable products. Quarterly technical progress report No. 12, June 1, 1996--August 30, 1996
Author(s) -
S. Komar Kawatra,
T.C. Eisele
Publication year - 1996
Language(s) - English
Resource type - Reports
DOI - 10.2172/415970
Subject(s) - scrubber , flue gas desulfurization , gypsum , flue gas , chemistry , lime , waste management , sulfur dioxide , sulfur , reagent , sulfate , wet scrubber , sodium sulfite , coal , sulfite , environmental chemistry , inorganic chemistry , metallurgy , sodium , materials science , organic chemistry , engineering
To reduce their sulfur emissions, many coal-fired electric power plants use wet flue-gas scrubbers. These scrubbers convert sulfur oxides into solid sulfate and sulfite sludge, which must then be disposed of. This sludge is a result of reacting limestone with sulfur dioxide to precipitate calcium sulfite and calcium sulfate. It consists of calcium sulfite, gypsum, and unreacted limestone or lime, with miscellaneous objectionable impurities such as iron oxides, silicates, and magnesium, sodium, and potassium oxides or salts. These impurities prevent many sludges from being utilized as a replacement for natural gypsum, and as a result they must be disposed of in landfills, which presents a serious disposal problem. Knowledge of scrubber sludge characteristics is necessary for the development of purification technologies which will make it possible to directly utilize scrubber sludges rather then landfilling them. This project is studying the use of minimal-reagent froth flotation as the purification process, using the surface properties of the particles of unreacted limestone to remove them and their associated impurities from the material, leaving a purified calcium sulfite/gypsum product. In this quarter, the installation of a laboratory-scale flotation column was completed. In addition to the installation of the flotation column, research on the determination of the surface properties of the components of the scrubber sludge was continued. Auger electron spectroscopy was investigated as a method for determining the composition of the first few monolayers of unreacted limestone and calcium sulfite/sulfate particles