In China, coal-fired power plants account for more than 70%, and it will generate a large amount of waste SO2 gas, which is very harmful for the environment. To solve the problem, usually treated by wet desulfurization. However, this method will cause huge wastewater. In order to reduce the concentration of harmful elements in the circulating slurry and corrosion and clogging to pipes, a certain amount of wastewater must be discharged, so that to ensure the stable operation of FGD system.
At present, the desulfurization wastewater treatment mainly are neutralization, sedimentation, flocculation and clarificatio. Then the sludge is dewatered by a plate frame filter press. The traditional process still contains a large amount of soluble salt. If it is reused, the suspended solids and Cl- may cause blockage and corrosion of the pipeline. If it is discharged directly, it might cause water deterioration and saline-alkali land.
In order to achieve “zero emissions”, the main goal is to soften water. Now, the main technologies include: (1) pretreatment + evaporation. (2) Pretreatment + membrane concentration + evaporation. (3) Pretreatment + membrane concentration + flue evaporation. However, the cost of existing technology is high. How to combine existing technologies, foster strengths and avoid weaknesses, so that can achieve zero-emission and improve the comprehensive utilization rate of wastewater and mineral salts, will be the key point in the future.