Behavior and fate of As, Se, and Cd in an ultra-low emission coal-fired power plant

Abstract

Environmental concerns regarding the toxicity of trace elements (TEs) and the harmful effects of these elements on humans have attracted worldwide attention. To meet stricter environmental policies, some coal-fired power plants have installed ultra-low emission equipment. In this paper, the behavior and fate of the trace elements As, Se, and Cd originating in an ultra-low emission coal-fired power plant equipped with air pollution control devices (APCDs), including selective catalytic reduction (SCR) equipment, a low-temperature economizer (LTE), an electrostatic precipitator (ESP), a wet flue gas desulfurization (WFGD) system, and a wet electrostatic precipitator (WESP), were investigated. Onsite samples of the feed coal, bottom ash, fly ash, gypsum, desulfurization slurry, WFGD effluent, WFGD-treated water, and WESP effluent were systematically collected and analyzed. The SCR and LTE configurations achieved a partial removal of As, Se, and Cd. The ESP trapped virtually all the particles and had a synergistic effect on the removal of the TEs. A systematic study of the recycling of the desulfurization slurry revealed TE enrichment in the WFGD system; because it concentrated in the liquid fraction of the gypsum slurry, Se was particularly susceptible to this enrichment. The effluent water treatment system achieved TE removal with efficiencies exceeding 94%. WESP operation achieved extensive removal of TE-enriched particles with percentages greater than 90%. The overall efficiencies of As, Se, and Cd removal obtained by the APCD system as a whole were 95.94%, 98.22%, and 92.70%, respectively.