Study On FGD Wastewater Evaporation Treatment

FGD wastewater is difficult to treat as its complex water quality and containing heavy metals. A new FGD wastewater treatment technology named evaporation tower was developed to realize FGD wastewater zero discharge.A small evaporation tower was built up to study its evaporation characteristics,evaporation products and the properties of uniform corrosion and evaporation products of different FGD wastewater of pH values,indicating that FGD wastewater evaporated in the center of the tower and the evaporation zone moved toward the direction of the tower wall and bottom with the increase of spray quantity. Meanwhile,fog moment enlarged with the increase of spray quantity and decreased with the rotational speed of atomizer.Finally,calculation showed that the treatment system had little effect on thermal system of power station as the amount of the flue gas extraction was controlled within 5%.FGD wastewater evaporation products include solid products and gaseous products. The main compositions in solid products are CaSO4?NaCl?Na₂SO₄ which can be analyzed by XRD. The main compositions in gaseous products are HCl,HF,HBr,HNO₂ and HNO₃,of which gaseous chlorine accounts for 2.7% of the total.The solid products have no bad effect on the comprehensive utilization of the fly ash,but it can increase the value of its specific resistivity.What's more, gaseous products such as HCl can aggravate corrosion of flue duct and increase the amount of FGD wastewater descharged.It's the best situation for the corrosion and amount of gaseous products when the pH value of FGD wastewater was about 9. Under this condition, the amount of evaporation products such as HF and HCl is small, which is beneficial to the solid transport of salts from FGD wastewater.The economical and technical aspects of evaporation tower system were analyzed,indicating that the technology is feasible and the ecomomy is superior.