Method for preparing FGD gypsum with improved brightness by organic acids having carboxylic group

摘要

PURPOSE: Provided is a method for preparing a flue gas desulfurized gypsum whose whiteness is improved by removing iron hydroxide and iron oxide effectively, to allow an organic acid to be reused continuously. CONSTITUTION: The method comprises the steps of contacting iron oxide and iron hydroxide contained in desulfurized gypsum lattice with an organic acid containing a carboxyl group to form a metal complex; dissociating the metal complex in a solution and separating a metal complex from gypsum by filtration washing; adding a reductant and a calcium-based compound to the filtered solution where an iron ion is dissolved, and controlling the pH to selectively separate and precipitate a calcium ligand compound and iron hydroxide; and reacting the calcium ligand compound with sulfuric acid and collecting it with an organic acid to reuse it continuously.