Study Of Activated Carbon Adsorbing Elemental Mercury In Coal-fired Flue Gas

Coal is one of main energy sources, and mercury emission in coal-fired flue gases becomes a significant environmental concern as it has done harm to human health. The problem is particularly severe for elemental mercury (Hg⁰) in vapor since it cannot be effectively removed using current air pollution control devices due to its low melting point, high equilibrium vapor pressure and low solubility in water. So it is necessary to take some measures to remove elemental mercury from flue gas effectively. After investigated some domestic and foreign technologies of removing Hg⁰, the experimental study of fixed-bed AC adsorbing Hg⁰ from flue gases has been finished in this paper.Results indicate that the adsorption efficiency is depending on the mass loading, carbon particle size, inlet Hg⁰ concentration, adsorption temperature and so on. The Hg⁰ removal efficiency increases when increasing the mass loading. However, low adsorption temperature and inlet Hg⁰ concentration could accelerate the rate of Hg⁰ removal. And suitable scale of carbon particle size (0.5max and the heat of adsorption ΔH_ads of different particle size carbon and different adsorption temperature are obtained. Results indicate that K and W_max decrease when increasing the adsorption temperature.In addition, this research uses HNO₃ and H₂O₂ to modify the carbon, 1%, 5% ZnCl₂ solution to impregnate chloride ion on the carbon, meanwhile, makes carbon heat-treated. The adsorption capacity of the heat-treated AC decreases while other modified ACs increase obviously. It indicates that the addition of chloride ion and oxygen group on carbon surface take good effects on Hg⁰ adsorption.