At present

the state encourages the use of flue gas evaporation technology to treat desulfurization wastewater from coal-fired power plants to achieve the goal of zero discharge of wastewater.The bypass evaporation tower process applies hot flue gas above 300℃to dry the wastewater.The wastewater contains a high concentration of chloride ions (Cl~–).During the evaporation process

a part of Cl~– generates hydrogen chloride which then enters the gas phase.The remaining Cl~– forms a crystalline salt with other ions

namely the solid evaporation product.Its mixing with fly ash may cause the Cl~– concentration exceeds the standard and affect the comprehensive utilization of fly ash.The equation of state method is employed to calculate the distribution of Cl~- between gas and solid phase.The chloride ion migration model of the evaporation tower is established.Combined with the actual data of a power plant in Guangdong

the model is used to calculate the chlorine content of the solid evaporation product.The results show that

the solid evaporation products are not hazardous wastes.However

due to the high chlorine content

it will have an impact on the production of building materials using solid evaporation products.It is recommended to use a high-temperature ceramic filter or a small electric precipitator to collect the solid evaporation products separately.The collected solid evaporation products are used in the production of concrete

non-burning bricks

or backfilling projects such as mines

highway subgrades and abutments.