A two-stage desalination process for zero liquid discharge of flue gas desulfurization wastewater by chloride precipitation

Yi Xin; Zhen Zhou; Qiang Ming; Dongqi Sun; Jun Han; Xiaofang Ye; Shifeng Dai; Lu-Man Jiang; Xiaodan Zhao; Ying An

doi:10.1016/j.jhazmat.2020.122744

A two-stage desalination process for zero liquid discharge of flue gas desulfurization wastewater by chloride precipitation

J Hazard Mater. 2020 Oct 5:397:122744. doi: 10.1016/j.jhazmat.2020.122744. Epub 2020 Apr 23.

Authors

Yi Xin¹, Zhen Zhou², Qiang Ming¹, Dongqi Sun¹, Jun Han³, Xiaofang Ye¹, Shifeng Dai³, Lu-Man Jiang¹, Xiaodan Zhao¹, Ying An¹

Affiliations

¹ Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, China.
² Shanghai Engineering Research Center of Energy - Saving in Heat Exchange Systems, College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai 200090, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China. Electronic address: zhouzhen@shiep.edu.cn.
³ Wujing Thermal Power Plant of Shanghai Electric Power Co., Ltd., Shanghai 200241, China.

PMID: 32361139
DOI: 10.1016/j.jhazmat.2020.122744

Abstract

A two-stage desalination process was developed to achieve zero liquid discharge (ZLD) of flue gas desulfurization (FGD) wastewater by precipitating chloride as Friedel's salt. Influential factors for Friedel's salt precipitation, including dosage, reaction time, concentration of sulfate, were investigate by batch tests. Batch results showed that at calcium to aluminum molar ratio of 3.0, the optimal chloride removal and the highest crystallinity of Friedel's salt were obtained. Sulfate impeded Friedel's salt precipitation by competitive inhibition mechanism, and thus calcium sulfate removal was designed in advance of chloride removal. Batch results and long-term results of bench-scale experiments showed that magnesium and part of sulfate were effectively removed by lime addition in Stage I of the proposed process, and then the remaining sulfate and 48.1 % of chloride were precipitated as ettringite and Friedel's salt in Stage II. The effluent of the two-stage process was alkaline with low turbidity, and had considerable desulfurization capacity. Techno-economic evaluation showed that the two-stage process is technically feasible, economically viable and environmentally friendly technology for ZLD of FGD wastewater.

Keywords: Chloride removal; Flue gas desulfurization wastewater; Friedel’s salt; Layered double hydroxides; Wastewater.

Publication types

Research Support, Non-U.S. Gov't