Analysis of Trace Elements in Flue Gas Desulfurization Water in the Coal Combustion System and the Removal of Boron and Mercury from the Water

A detailed analysis was performed on the slurry supernatant water obtained from a wet flue gas desulfurization (FGD) system in a pilot plant of a coal combustion facility using five different coals. The determination of trace elements in those samples was performed by use of inductively coupled plasma–atomic emission spectrometry (ICP–AES), inductively coupled plasma–mass spectrometry (ICP–MS), and other methods, while the analysis of major cations and anions was conducted by ICP–AES and ion chromatography, respectively. The levels of B, Se, and Hg in the FGD water were sometimes high (44–62 mg/L for B, 0.24–0.37 mg/L for Se, and 0.11–0.23 mg/L for Hg), and these values exceeded the Japanese national effluent standards for terrestrial water (10, 0.1, and 0.005 mg/L for B, Se, and Hg, respectively). Simulated FGD water was prepared as a result of the analysis mentioned above, and the removal of those hazardous elements was attempted using various adsorbents, including N-methylglucamine resins (DIAION CRB02 and CRB05), a N-methylglucamine fiber (Chelest fiber GRY-L), an iminodiacetic acid resin (DIAION CR11), a polyamine resin (DIAION CR20), an anion-exchange resin (DOWEX 1X8), activated alumina, and activated carbon. For the simultaneous removal of B and Hg from the simulated FGD water, which contained 60 mg/L of B and 0.11 mg/L of Hg, CRB02 was the most effective and the percent removal values for B and Hg were 88 and 97%, respectively. The resulting water met the effluent standards.