Mass flows and characteristic of mercury emitted from coal-fired power plant equipped with seawater flue gas desulphurization

Abstract

This study investigated the characteristics of mercury emitted from a large-scale coal-fired power plant in Taiwan via intensive sampling campaigns. The air pollution control devices equipped in this coal-fired power plant include selective catalytic reduction, fabric filter and seawater flue gas desulfurization. During three sampling campaigns, mercury concentrations emitted from this large-scale coal fired power plant ranged from 0.04 to 0.35 μg Nm−3. In addition, solid and liquid samples including coal, bottom ash, fly ash and inlet/outlet seawater were collected and analyzed for mercury content to provide the mass flows of mercury in this plant. The results indicate that mercury emitted from this coal-fired power plant is dominated by Hg0, and the emission factor of mercury ranges from 0.37 to 3.37 mg Hg t−1 coal, which is relatively lower than those reported in other studies. The relative enrichment factor of mercury in fly ash (0.23–1.22) is significantly higher than that of bottom ash (0.10 × 10–3–0.89 × 10–3). Although this coal-fired power plant has a relatively low mercury atmospheric emission which accounts for 6.4% of the total mercury output, it is essential to further control mercury released from fly ash (62.6% of the total mercury output) and discharged seawater (33.7% of the total mercury output) to reduce environmental damage and human health effects.