Comparison of mercury emission from around 300 MW coal-fired power generation units between pulverized boiler and circulating fluidized-bed boiler

The mercury emission characteristics are investigated and compared at a coal-fired power plant with 330 MW pulverized coal (PC) boiler and a coal-fired power plant with 350 MW circulating fluidized bed (CFB) boiler. EPA 30B method and Ontario method were used to test the mercury concentration in flue gas at the inlet of dust extraction unit, outlet of dust extraction unit, outlet of desulfurization unit, and outlet of wet dust extraction unit. The feed coal, bottom ash, fly ash and gypsum sample were collected at the same time together with gas sampling. The effect of the existing air pollution control device on mercury control was discussed toward PC and CFB units based on the mercury distribution data. The results show that the mercury concentration at fabric filter (FF) outlet of CFB power plant is decreased to 0.43 μg/m³ and the mercury removal efficiency of FF reaches 98.9%. A predominating portion of mercury is enriched in fly ash. With respect to a PC power plant, the mercury concentrations at inlet and outlet of ESP are both higher than those in the CFB power plant, and the mercury concentration gradually drops from electrostatic precipitator (ESP) inlet to wet flue gas desulfurization (WFGD) outlet. The mercury concentration reaches a low value of 0.42 μg/m³ at the WFGD outlet, and the mercury removal efficiency of ESP and WFGD is 75.0% and 22.4%, respectively, which can meet the ultra low mercury emission controlling.