Behavior of selenium in the flue gas of pulverized coal combustion system: Influence of kind of coal and combustion conditions

•The behavior of Se in a coal combustion system was examined.•Se in the flue gas was satisfyingly recovered by ISO method for low Se level coals.•Se in the solid phase increased with a decrease in the flue gas temperature.•Se was physically adsorbed on the coal ash surface in low temperature.•Se was chemically adsorbed on the coal ash surface in high temperature.

Five kinds of coals (mainly low Se levels) were pulverized and combusted in a turbulent furnace combustion test rig, which had a burner on the top and a gas cooling pipe with two sampling ports at the side near the bottom. A sampling train according to ISO 17211:2015 was attached to the ports to assess the distribution of Se in the gas and solid phase (coal ash) in the flue gas. The fraction of Se in the solid phase (R Ses) in the flue gas is given by R Ses = Ses/(Ses + Seg), where Ses and Seg are the concentrations of Se in the solid and gas phases, respectively. For all coals, R Ses increased with a decrease in the flue gas temperature from 300 °C to 100 °C, and the difference in R Ses by the temperature was greatly dependent on the kinds of feed coals. The effects of the contents of minerals in feed coals and the combustion conditions upon R Ses were studied. The partitioning of Se from the gas to solid phase in the flue gas was elucidated in terms of the chemical and physical adsorption of Se on coal ash.