The release and behavior of mercury, selenium, and boron in coal combustion

The release of mercury, selenium and boron from coal is investigated at high temperatures using a drop tube furnace and a coal combustion test facility. The results show that under combustion conditions, most of the mercury and selenium are released from the coal and did not remain in the fly ash at high temperatures, but some of the boron remains in the fly ash at high temperature. Under reducing conditions, all of the mercury is released from the coal, and some of the selenium and most of the boron remains in the coal char at 1473 K. This indicates that oxidation reaction contributes to the release of selenium and boron from coal. The transfer of these elements from gas to fly ash in coal combustion is tested as a function of temperature. The results show that mercury and selenium are captured on fly ash below 773 K, and the capture ratio increases as the temperature decreases. The transfer of boron from gas to fly ash is small between 393 K and 1273 K.