Lead: Limestone - gypsum method is currently the most widely used flue gas desulfurization boiler. The wastewater generated in the desulfurization process is mainly from waste water discharged from the absorption tower, waste water from the gypsum dehydration and cleaning system. The impurities contained in wastewater mainly include suspended solids, supersaturated sulfites, sulfates and heavy metals, many of which are the first type of pollutants that are subject to strict control in national environmental standards. Wastewater treatment process: a wastewater neutralization (alkalization) a settlement of a flocculation of a clear a clear water (pH adjusted to 6 to 9 range) Wastewater neutralization The reaction tank is composed of three compartments. Each compartment is full of gravity and enters into the next compartment. When desulfurization wastewater enters the first compartment, a certain amount of milk of lime (5% -10% concentration) , By constant stirring, its pH value can rise from 5.5 to 9.0 above. Heavy metal precipitation The addition of Ca (OH) 2 not only raises the pH value of the wastewater, but also makes the heavy metal ions such as Fe3 +, Zn2 +, Cu2 +, Ni2 + and Cr3 + form hydroxide precipitates. In general, the trivalent heavy metal ions are more likely to precipitate than the divalent ions, and most of the heavy metal ions form insoluble hydroxides when the pH reaches 9.0-9.5. At the same time, Ca2 + in lime slurry can react with part of F in waste water to form insoluble CaF2; complex with As3 + to form insoluble substance such as Ca (As03) 2. At this point pb2 +, Hg2 + remain in ionic form in the waste water, so adding organic sulfide in the second compartment, make it react with Pb2 +, Hg2 + to form insoluble sulfide sediment {organic sulfides TMT-15 product concentration 15% according to the proportion of waste water dosing). 3 flocculation reaction After the first two steps of chemical precipitation reaction, the wastewater also contains many fine and dispersed particles and colloids, so add a certain proportion of the third tank flocculant FeCIS04, so that they condensed into large particles and deposited in the Waste water reaction tank outlet plus cationic polymer polyelectrolyte as a coagulant to reduce the particle surface tension, strengthen the growth process of particles to further promote the precipitation of hydroxides and sulfides, so that small floes slowly Become larger, more easily deposited flocs, while the desulfurization wastewater suspended solids also settled down. In the flocculation system, add FeCISO4 and polymerization dielectric (coagulant) to increase the flocculation, improve the clarification effect. FeCISO4 40% of liquid products, according to the proportion of waste water dosage; coagulant added to a concentration of 0.1%.