In the present study, the behavior of mercury (Hgp) in solid particles collected from a very cold electrostatic precipitator (VCEP) with the flue gas temperature of 94°C in a large scale pulverized coal power plant in Japan was examined for ten different coal samples. In addition, the investigation of the Hgp content for each particle size in five fly ashes clarified the effect of the particle size of unburned carbons on the Hgp content in fly ash. As a result, the distribution of Hgp into fly ash collected from the VCEP was 13.6-92.3% and increased with the unburned carbon (0.49-2.84%) in fly ash. The decrease of the flue gas temperature heightened the effect of the unburned carbon on the Hgp content in fly ash. The shift of approximately 0.2% in the content of the unburned carbon in fly ash led to the change of 5 - 15% in the distribution of Hgp into fly ash. The increase of the particle size of fly ash heightened the contents of Hgp and the unburned carbon in fly ash. This suggested that the particle size of the unburned carbon in fly ash significantly affected the formation of Hgp.
