The terminal waste-water should be pretreated using evaporation crystallization technology in a zero-liquid discharge coal-fired power plant with a dry ash removal system.Because of the complexity of composition and the worst quality of waste-water from flue gas desulphurization(FGD) system

it is very hard to pretreat the FGD waste-water using the evaporation crystallization technology.Based on the quality features of FGD waste-water and the requirements of intaking water quality for evaporation crystallization

a two-stage chemcial sedimentation technology has been designed for treatmetn of the FGD waste-water.Study shows that the adding of Ca(OH)2 into the first stage chemical sedimentation to maintain the pH value in an approciate range

and the adding of Na2CO3 into the second stage chemical sedimentation

as well as the adding of FeCl3 and polyarylamide(PAM) into both stages

can make the Ca2+

Mg2+

SO2-4

and Si content in the effluent water to reach the requirement of intaking water quality for the evaporation crystallization technology.