Abstract: As the final stage of the FGD wastewater treatment and discharge process in the power plant, sludge dewatering may affect the whole wastewater processing system operation if it is not designed reasonably or operated properly. There are two kinds of sludge dewatering devices, the frame filter press machine and the centrifugal dewatering machine. In a power plant, the centrifugal dewatering machine is originally adopted in the desulfurization wastewater sludge treatment and the produced cake contains more than 80% of water and presents semi-fluid state, causing secondary pollution in the process of loading/unloading and transportation. Therefore, the dewatering system is modified by replacing the original dewatering centrifuge with the frame filter and installing the sludge buffer tank, sludge circulation pump and sludge feed pump. The comparative study on the dewatering devices before and after the modification is conducted. The study results show that the frame filter is more suitable for the desulfurization wastewater sludge treatment process. The mass fraction of the dewatered cake solid is higher than 30%, and the operation of the system is stable with lower energy consumption.

Key words: limestone-gypsum wet desulfurization, FGD wastewater, frame filter, centrifugal dewatering machine, solid content of the sludge, settling velocity