A method and apparatus for reducing mercury in industrial gases such as the flue gas produced by the combustion of fossil fuels such as coal adds hydrogen sulfide to the flue gas in or just before a scrubber of the industrial process which contains the wet scrubber. The method and apparatus of the present invention is applicable to installations employing either wet or dry scrubber flue gas desulfurization systems. The present invention uses kraft green liquor as a source for hydrogen sulfide and/or the injection of mineral acids into the green liquor to release vaporous hydrogen sulfide in order to form mercury sulfide solids.
 The subject matter of the present invention was developed under a research contract with the U.S. Department of Energy (DOE), Contract No. DE-FC22-94PC94251, and under a grant agreement with the Ohio Coal Development Office (OCDO), Grant Agreement No. CDO/D-922-13. The governments of the United States and Ohio have certain rights in the invention.