Advances in mercury removal from coal-fired flue gas by mineral adsorbents

Mercury emissions from coal-fired power plant flue gas (CFFG(1)) threaten the natural environment and human health, and this has attracted the attention of environmental protection departments and scientific researchers in recent years. Mineral adsorbents perform well at mercury removal and extensive studies on them have been conducted. This review discusses the progress in researching the application of mineral adsorbents to mercury emission control technologies applied to CFFG. The species and physicochemical characteristics of some common mineral adsorbents are briefly introduced and various modification methods, mainly including high temperature activation, acid activation, organic modification, inorganic modification and combinations of modifications, are summarised. As well, the mercury removal performance of various mineral adsorbents is evaluated, and the results indicate that removal performance relates to the actions of the mineral carrier combined with modification methods which are able to improve the physical structure of minerals and/or increase the number of active sites for mercury removal on the mineral surfaces. The effects of the main process parameters, including reaction temperature and flue gas components (O-2, HCl, SO2, NO, H2O, Hg-0, etc.), on mercury removal by different mineral adsorbents are also systematically reviewed. Moreover, the possible adsorption and oxidation approaches involved in the process of mercury removal by mineral adsorbents are discussed. This review indicates that the chemical active site is the key factor for mercury removal. Our economic evaluation indicates that the cost of mineral adsorbent is much lower than that of activated carbon, showing that mineral adsorbents have promise in terms of industrial applications. Finally, future work necessary for the continued development of mineral adsorbent injection technology for CFFG mercury control is proposed.