Wet Type Flue-Gas Desulfurization Method

A wet type flue-gas desulfurization method for desulfurizing by using a wet type flue-gas desulfurization apparatus comprising:

• an apparatus body side absorption tower which has an apparatus body side circulation tank in a lower portion thereof, the apparatus body side circulation tank reserving absorbent slurry;
• an apparatus body side absorbent spray nozzle which is placed inside the apparatus body side absorption tower to spray the absorbent slurry;
• an oxidation gas supply portion which supplies oxidation gas to the absorbent slurry reserved in the apparatus body side circulation tank;
• and
• a desulfurization apparatus body which includes the apparatus body side absorption tower, the apparatus body side absorbent spray nozzle and the oxidation gas supply portion, and in which gas to be treated, containing sulfur compounds, is introduced into the apparatus body side absorption tower and brought into gas-liquid contact with the absorbent slurry sprayed from the apparatus body side absorbent spray nozzle, so that the sulfur compounds in the gas to be treated can be absorbed by the absorbent slurry;
• wherein:
• the gas to be treated contains mercury;
• the desulfurization apparatus is provided with, on an upstream side of the desulfurization apparatus body in a flow direction of the gas to be treated:
• an upstream absorption tower which includes an upstream circulation tank reserving absorbent slurry;
• an upstream absorbent spray nozzle which is placed inside the upstream absorption tower to spray the absorbent slurry;
• and
• a make-up water supply unit which supplies make-up water into the upstream circulation tank to keep a chloride ion concentration of the absorbent slurry in the upstream circulation tank not lower than 50,000 ppm, the upstream absorption tower, the upstream absorbent spray nozzle,
• the method comprising the acts of:
• collecting liquid by an upstream mist eliminator provided between the upstream absorbent spray nozzle and the desulfurization apparatus body;
• and
• returning the collected liquid obtained by the upstream mist eliminator to the upstream absorption tower.