Study On Mercury Removal In Coal-fired Flue Gases By Modified Non Carbon Sorbents

Active carbon injection technology is the most useful way to remove mercury from coal-fired gases at present.But active carbon injection can cause higher cost and deterioration of flying ash's quality.So non carbon sorbents become hot spots worldwide as substitutes to active carbons.A new way of using lots of modified mineral sorbents and Fe3O4-Ag nanoparticles to remove mercury is raised in this paper.Many non carbon sorbents with high specific area and high pore volume were made to remove mercury in simulated flue gases or in coal-fired gases generated by a fluid-bed boiler.The results can be theoretical and experimental bases to further research about coal-fired mercury control.Modified zeolites,attapulgites,bentonites,aluminum oxide and kaolines were chosen to remove mercury in simulated flue gases.The results show that Mn-zeolites,Mn-attapulgites,Mn-bentonites,Co-bentonites and Mn-aliuminum oxide show excellent adsorption capability among all mineral sorbents with high mercury removal efficiencies as 85.6 percent,82.5 percent,87.9 percent,83.5 percent and 81.6 percent.To Mn-zeolites,Mn-attapulgites,Mn-bentonites and Co-bentonites,optimum working temperature is 200 ? while optimum working temperature is 300 ? to Mn-aluminum oxide.Modified kaolines are improper sorbents because of low mercury removal efficiencies and temperature sensibility.Magnetic Fe3O4 nanosorbents wrapped by Ag were made.The results show that Fe3O4-Ag structure improves the adsorption capability of sorbents and the mercury removal efficiency is higher than 90 percent.Modification doubles the average pore size and pore volume of nanoparticles and increases the specific area at the same time.Experiments of repeating adsorption and desorption show that every time of adsorption shows high mercury removal efficieny.Fe3O4-Ag nanoparticles are separable because of magnetic properties.So Fe3O4-Ag nanoparticles have bright prospects to lower mercury removal costs.A medium sized fluid-bed boiler experimental system with holonomic contamination control equipments was built.Based on adsorption experiments on the fixed-bed,mercury removal performances of some excellent modified mineral sorbents and commercial active carbons were compared.The results show that modified mineral sorbents can remove more than 70 percent of mercury in the fluid-bed gases which are better than active carbons.