Partitioning of Hazardous Trace Elements among Air Pollution Control Devices in Ultra-Low-Emission Coal-Fired Power Plants

In this work, the partitioning of hazardous trace elements among air pollution control devices in five ultra-low emission coal-fired power plants was investigated. Results showed that most of the trace elements were enriched in fly ash at 58.0-93.3% (Hg), 75.2-95.3% (As), 78.2-94.9% (Cd), 79.4-96.6% (Se), 73.8-89.2% (Cr), and 86.5-99.5% (Pb). A low-low temperature electrostatic precipitator (LLT-ESP) and electric fabric filter (EFF) greatly increased the relative enrichment factors of Hg, As, and Se in fly ash up to 0.78-1.23, 0.85-1.04, and 0.83-0.99, respectively. In the wet flue gas desulfurization (WFGD) system, the concentrations of trace elements in fine fractions were much higher than those in coarse fractions. Large amounts of Hg (2.17-168 mu g/kg), Se (21.3-357 mu g/kg), and Cd (44.1-839 mu g/kg) in wastewater needed special treatment to satisfy the discharge standard. The wet electrostatic precipitator (WESP) system removed hazardous trace elements mainly by capturing fine particles in the flue gas, and a small amount, of hazardous trace elements (0.2-26%) were retained in the washing water. The concentrations of Hg in the fine particulates captured by WESP were 16.8-60.1 times of those in the fly ash, which could reach up to 17.5 mg/kg. The application of selective catalytic reduction + LLT-ESP/EFF + WFGD + WESP could effectively control the emission of hazardous trace elements in coal-fired power plants.