Separation of flue-gas scrubber sludge into marketable products. Third year, second quarterly technical progress report, December 1, 1995--February 29, 1996 (Quarter {number_sign}10)

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. Knowledge of scrubber sludge characteristics is necessary for the development of purification technologies which will make it possible to directly utilize scrubber sludges rather than 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 the current quarter, research was focused on two different areas. The first part of this quarter the optimization of the feed slurry percent solids for the two inch water-only cyclone was completed. The optimization of the vortex finder, spigot diameter and inlet feed pressure was completed in the previous quarter. The second part of this quarter began the investigation of why water-only cycloning helps froth flotation performance. The hypothesis is that water-only cycloning scrubs the surface of the unreacted limestone. This scrubbing effect provides a clean calcium carbonate surface, which results in better flotation reagent adsorption. This study used the scanning electron microscope to investigate the surface of the unreacted limestone particles