Abstract：In this paper, two determination methods of calcium sulfate dihydrate in limestone/gypsum wet FGD system are introduced by comparing the existing gypsum analysis standards in China and combining with practical application；In order to demonstrate the test temperature value selected by ignition gravimetric method, 380℃was selected as the test temperature value in this study, three FGD building gypsum phases were analyzed. The dehydration process of dihydrate gypsum has no clear phase change rule from the calcination temperature of 220 ℃, suggesting that the hydration property is unstable and the quality is not easy to control; At the same time, the standard method was used to test the specific gravity determination method and the improved ignition gravimetric method, and the accuracy and precision were compared. The t-test showed that there was no significant difference between the two analytical methods at the 95% confidence level.
