The Experimental Study Of Mercury Emission And Control In Coal-fired Power Plants

The samples of coal, bottom ash and fly ash were collected from three coal-fired power plants in the city of Huainan. The concentrations of mercury in these samples were analyzed and its corresponding enrichment factors (EF) of mercury were calculated. The Flow Injection Mercury System (FIMS, PERKIN ELMER As90) for testing mercury was used. In addition, XRD, SEM and SDT were used for samples characterization.The experimental results show that raw coal in the three coal-fired power plants has an average mercury concentration of 0.30mg/(kg coal), higher than average mercury value of coal China(0.19mg/(kg coal)). The measured average mercury concentration in bottom ash is 0.06mg/(kg bottom ash), electrostatic precipitators(ESP) installed at the coal-fired power plants have efficiency on controlling mercury emission, and the measured average mercury concentration in fly ash is 0.35mg/(kg fly ash). Mercury concentration in WFGD slurry reaches 3.73 mg/(kg slurry).The calculated results of enrichment factors (EF) of mercury show that WFGD has the best enrichment efficiency, followed by fly ash, and bottom ash correspondingly. Therefore, the WFGD device could give more contribution to the mercury control, and should be regarded as an effective control method of mercury pollution. Hg0, a stable speciation, will not readily solubilize in water, hence it's difficult to be collected by WFGD and will be emitted with the flue gas into the air directly. Sorbent injection or transformation of Hg0 into Hg2+ should be used for Hg0 control.Based on the experimental results, some suggestions and expectations for mercury control in coal-fired power plants are given.