Some of the less recent patents relating to FGD treatment of flue gases

US Patent No. 6,946,108 describes an invention with an FGD arrangement that uses activated carbon sheets to wick water to the surface of the sheets which are exposed to flue gas for the production of sulfuric acid.

US Patent No.  6,726,748 is entitled “Method of converting a downflow/upflow wet flue gas desulfurization (WFGD) system to an upflow single-loop WFGD system.”

US Patent No.  6,555,082 describes an invention with air oxidation of calcium based FGD compounds.

US Patent No. 6,569,395 describes an invention having a flue gas desulfurization system that treats cooled flue gas with aqueous ammonia.

US Patent No. 6,217,766 describes an invention with anaerobic bacterial reduction of sulfur compounds in FGD blow-down.