Modified Non-carbon Sorbents With Mno₂ And Br₂ For Mercury Removal From Simulated Flue Gas

Mercury emission from the coal combustion process is the main source of atmospheric mercury pollution. Adsorption of mercury by sorbent injection is a simple way of removal mercury after combustion. Because of its high cost, activated carbon is not widely used in coal-fired power plants for mercury removal. So it's necessary to develop non-carbon-based adsorbent technologies.In the thesis, a fixed-bed furnace and a laboratory-scale drop tube furnace were used to investigate influence of temperature and mercury concentration on the capture efficiency. Also influence of type of sorbents, such as kaolin, zeolite and limestone, and their modification by MnO₂ and Br2 on the capture ability was discussed.The results on experiments of fixed-bed show that, modified sorbents have larger absorption force than the original especially for the Br-impregnated sorbents used. Experiments at various given temperature of 75℃,125℃and 175℃also show that, the absorbing force of the original sorbents tends to be lowest at 75℃and decreases with the increase of temperature by inhibiting significant physical absorption effect. However, it is quite different for modified sorbents used, in which the absorbing force is largest at 175℃and tends to be positive with temperature by exhibiting significant chemical absorption. The experiments also demonstrate that, with the increase of inlet mercury concentration, absorption force increases with 60% used for MnO₂ modification, while 35% for Br2 modification.The results from experiments in laboratory-scale drop tube furnace shows that, modified sorbents have better absorbing activity than the original, which is uniform with experiments on fixed-bed. When absorbent addition increases from 0.25 g/min to 0.35 g/ min, absorption force of all the absorbents becomes larger and within which MnO₂ modification has the largest increase amplitude. Moreover, experiments by adding inlet mercury concentration from 1.6μg/m³ to 2.0μg/m³ also shows that absorption effect for all sorbents is influenced by inlet mercury concentration by some extent, among which the kaolin is most sensitive, zeolite less and limestone least, which can be also demonstrated in experiments performed on fixed-bed.