Abstract: It is expected to achieve low-cost zero discharge of FGD wastewater by using MED or MSF technology driven by different heat sources of the power plant. In this paper, five different combinations of schemes are proposed for the desulfurization wastewater pretreated in the “pretreatment-concentration-evaporation desalination” process to achieve the target of "concentration-deep desalination". The thermal economic analysis model of each scheme was established respectively, and the change rules of gained output ratio (GOR) and heat cost was also quantitatively studied. The results show that as far as the heat source is concerned, the cost of auxiliary steam is higher, while the cost using the waste heat of the flue gas is cheaper with the pumping power becoming the major cost contributor. With the TVC device installed, the GOR of MED can be improved by 10%~100%, and the heat cost can be reduced by about 10%~50%. However, in addition to its high sensitivity to fluctuations in wastewater salt concentration, the structure of the MED structure is not suitable for treating high salt concentration wastewater. In contrast, the MSF structure demonstrates high adaptability to salt concentration. The heating cost of using flue gas heating is about 0.3~1.2 yuan/t.

Key words: desulfurization wastewater, zero discharge, MED, MSF, thermal cost, economic deposition