Study On Oxidation Of Mercury In Coal-Fired Flue Gas By Catalyst For Denitrification Oxidation

Energy is an important factor in national development,while coal is China’s main primary energy.Mercury removal methods in the future should be effective and can be widely spreaded,which means higher efficiency,lower cost and low secondary pollution.Chemical reaction process of mercury in flue gases is not clear.Efficient mercury removal technologies require active development works.Commercial SCR catalysts were used for mercury oxidation experiments.Factors such as temperature and flue gas composition were tested for their effects on the oxidizing ability of the catalysts.Commercial SCR catalysts are efficient for elemental mercury oxidation in simulated flue gas.Temperature is an important factor for mercury oxidizing.NO and HCl enhance the oxidizing ability while SO2 inhibits the oxidizing ability.Pilot experiment was designed to study the mercury oxidation performance of SCR catalysts about engineering practice in 0.3MW circulating fluidized bed.Mercury oxidation capacity of the catalyst decreases while ammonia-nitrogen ratio increases,but its denitrification efficiency is improved.Mercury removal efficiency of the catalyst decreases while the ammonia injection rate increases,and it increases with the temperature on the pilot test bed increasing.Amount of particulate mercury in the flue gas unchanges after passing through the SCR catalysts.Meanwhile,Hg0 concentration decreased,and Hg2+ concentration increased.Modification experiment was designed against the weakness of SCR catalysts.New catalysts were obtained by modifying the SCR catalyst with CuCl2 and CrC13.CuCl2/SCR catalysts have high oxidation performance.Oxidation rate of Hg0 increases with the concentration of HCl,increasing with CuCl2 loading in the catalysts increasing,decreasing with SO2 concentration increasing.Oxidation efficiency of catalysts modified by CrCl3 increases with increasing temperature.Mercury oxidation rate of the catalysts increases with the increase of CrCl3 concentration.O2 and HCl have a positive effect on the oxidation of new catalysts.CuCl2 modified catalysts mercury oxidation performance is better than CrCl3 element modified catalysts,whose SO2 resistance is bad than CrCl3 modified catalysts.Introduction of chloride modification solve the problem of low Hg0 oxidation rate in chlorine Coal-fired flue gases.