Mercury in desulfurization gypsum and its dependence on coal properties in coal-fired power plants

To disclose possible influencing factors on mercury (Hg) contents in flue gas desulfurization (FGD) gypsum of coal-fired power plants (CFPPs), 11 major CFPPs in Guizhou province of southwest China were surveyed for analyzing Hg contents in feed coal, limestone and gypsum as well as coal properties. It was found that Hg contents in the desulfurization gypsum of the 11 CFPPs varied greatly from 160 to 1482 mu g kg(-1), with an average of 595 +/- 353 mu g kg(-1). The majority of Hg in gypsum was introduced from the flue gas downstream of the particulate matter control devices, while a much lesser portion (average 3.43 +/- 3.85%) was stemmed from limestone. Hg content in gypsum has a strong positive correlation with chlorine content, a weak positive correlation with Hg content and a weak negative correlation with sulfur content in feed coal. Multiple regression analysis results showed that Hg and Cl contents in feed coal were the major determinants of Hg content in flue gas FGD gypsum despite the proportioning of Hg went in wet FGD system was not been evaluated. Results from the present study suggested that coal characteristics are important factors affecting Hg contents in gypsum.