System for processing mercury in flue gas

1. A system for removing Hg contained in flue gas from a boiler, the system comprising:

a heat exchanger for performing heat exchange of the flue gas from the boiler;

a precipitator for removing soot and dust in the flue gas;

a wet desulfurization device for removing mercury oxide Hg 2+ in the flue gas with a limestone and gypsum slurry, the wet desulfurization device including a circulation line for circulating the limestone and gypsum slurry;

a water supply line for supplying water containing reductive and humic material to the wet desulfurization device; and

a removal assistant supply unit that supplies a removal assistant for removing the reductive and humic material to the water supply line or circulation line.

2. The system according to claim 1 , further comprising a denitration unit having a denitration catalyst for oxidizing metallic mercury)(Hg 0 ) by denitration of NOx in the flue gas.

3. The system according to claim 2 , further comprising a reduction oxidation assistant supply unit that supplies a reduction oxidation assistant to a flue gas duct in the downstream of the boiler,

wherein NOx in the flue gas is reduced with the reduction assistant by the denitration unit and the metallic mercury)(Hg 0 ) is oxidized in the coexistence of an oxidation assistant.

4. The system according to claim 1 , wherein the removal assistant supply unit supplies a plurality of types of removal assistants.

5. The system according to claim 1 , wherein a supply amount of the removal assistant is determined by an oxidation reduction state of the limestone and gypsum slurry.

6. The system according to claim 1 , wherein an oxidation reduction state in the desulfurization device is determined by oxidation reduction potential (ORP) of the limestone and gypsum slurry or sulfurous acid ion (SO 3 2− ) concentration.

7. The system according to claim 1 , wherein a plurality of types of removal assistant are used.