Mercury in a coal-fired power plant equipped with a selective catalytic reduction(SCR)reactor can be effectively captured by its wet flue gas desulfurization(WFGD)system.However,Hg0 re-emission in WFGD can reduce mercury removal efficiency significantly.Additives can react with mercury and inhibit Hg0 re-emission effectively.The mercury sequestrated on gypsum by the additives may be released into atmosphere by thermal treatment during gypsum production,The effects of various additives(TMT,DTCR and NaHS)used in the gypsum slurry on mercury release in the drying process and simultaneous transformation of Hg species in gypsum were studied to evaluate the application of additives scientifically.In this study,firstly the effect of inhibiting Hg0 re-emission and mercury sequestration by additives in the gypsum slurry was discussed.Secondly simulated gypsum drying experiments were conducted to estimate in the drying process additives influence the mercury release of gypsum.Finally temperature-programmed experiments which are to evaluate changes of Hg compound species in gypsum were carried out to demonstrate behaviors of the mercury release of gypsum.The results showed all additives could inhibit Hg0 re-emission in slurry significantly.The mercury content of gypsum which was obtained from gypsum slurry with TMT was the highest and the mercury content in the filtrate of gypsum slurry with TMT was the least so that the effect of mercury sequestration by TMT was the best.NaHS had the worst effect on mercury sequestration in gypsum slurry.The addition of NaHS could improve thermal stability of mercury in gypsum in follow-up drying process,but thermal stability of mercury deteriorated after the TMT or DTCR was added.Although TMT and NaHS made the mercury content of gypsum were the highest and the lowest,respectively,but after drying the mercury content of gypsum which was obtained from gypsum slurry with NaHS and TMT were the highest and lowest,respectively.Temperature-programmed experiments showed when NaHS,TMT and DTCR were add to gypsum slurry,Hg compounds in gypsum were mainly formed HgS,Hg3(TMT)2 and Hg(DTCR)2,respectively.The peak temperature of decomposition and the range of decomposition temperature is gradually reduced in the order of HgS,Hg3(TMT)2 and Hg(DTCR)2,resulting the mercury content of gypsum with addition of DTCR was the lowest levels after drying.This study made a research on mercury pollution in the gypsum drying process and provided advices to actual use of additives.