Bench-scale experimental study on the effect of flue gas composition on mercury removal by activated carbon adsorption

This paper outlines the results of a systematic study on the capture of trace mercury vapor from simulated flue gases, using activated carbons. The experiments were conducted on a bench-scale fixed-bed test rig with intensive focus on the variable flue gas components and compositions. To understand the interaction and competitive adsorption of different gas components well, these gases (O-2, CO2, SO2, and moisture) were introduced, one by one, into the simulated flue gas system, which basically contained only nitrogen and elemental mercury vapor. The performances of five commercially available activated carbons and one prepared H2S-exhausted activated carbon were evaluated under different flue gas compositions. The experimental data suggested that the adsorption of mercury is greatly dependent upon the flue gas compositions. For sulfur-impregnated carbon, adsorption capacity is more constant than virgin carbon over a wide range of humidities and CO2 and SO2 concentrations. The H2S-exhausted activated carbon demonstrated an even better performance than the virgin carbon. Furthermore, the chemistry and related potential carbon surface reactions were discussed in-depth for a better understanding of the impact of variable flue gas components on the capacity of activated carbons for mercury removal in the simulated coal-fired flue gases.