A total flue gas mercury(Hg)removal system by injecting the halide additives to the coal outside the furnace was established in a domestic industrial unit and a series of tests were carried out.The Hg concentrations in the coal

slag

fly ash

desulfurized gypsum

desulfurized water and flue gas were measured before and after the installation of the system

and Hg balances of the unit were investigated thoroughly.The total Hg and its different forms content were measured before and after the wet flue gas desulfurization(WFGD)by adsorption tubes.The operation of the experimental system has lasted for over one year under optimized condition to ensure credible Hg removal results

and the practical operation cost can be obtained.It is revealed that after injecting the halide additives

the mass ratio of Hg2+to the total Hg before the WFGD increased significantly from 30%to 80%.The Hg removed by the WFGD and fly ash was enhanced by 0.9and 1.5times

respectively.The overall Hg removal efficiency increased from 33%to 90%

and the Hg emitted from the flue gas reduced from 2.21μg/m3 to 0.26μg/m3.Simultaneously

the operation cost of the unit only increased by about RMB 0.05cent/(kW·h).