With the continuous improvement of China′s environmental protection policies and the serious lack of water resources,the deep treatment of flue gas desulfurization (FGD) wastewater and water recovery are of great significance. In the present work,an overall zero liquid discharge (ZLD) process system for FGD wastewater was constructed,and three kinds of thermal concentration processes were proposed:multi-effect evaporation system (MEE),single stage mechanical vapor recompression system (MVR-S) and multi-effect evaporation system coupled with MVR (MEE-MVR). MEE includes multi-effect evaporation system driven by live steam and multi-effect evaporction system driven by low-temperature flue gas.Taking a 600 MW supercritical unit as an example,process simulation and system economics calculation were carried out using Aspen Plus software.The results show that compared with the traditional multi-effect evaporation system driven by live steam (MEE-S),the temperature of the flue gas is reduced by 5.5 ℃ when the low-temperature flue gas is used as the heat source. If the cost of the low-temperature flue gas is ignored,the cost of wastewater treatment per ton is lowest. The energy consumption of single-stage MVR system is greatly reduced due to the use of heat pump evaporation technology,but the investment cost is 113% of MEE-S system. For the MEE-MVR system,the power consumption of the compressor is reduced by 30% compared with the MVR-S,and the cost of wastewater treatment per ton is about 58.2% of the MEE-S system.