[Subject] To effectively utilize coal ash while reducing mercury concentration in cement kiln exhaust gas.
[Means for Solution] Coal ash is received from a thermal power plant or the like; the received coal ash is separated into ash and unburned carbon; the separated ash is utilized in a cement manufacturing facility as a cement raw material; and the separated unburned carbon is utilized in the cement manufacturing facility in accordance with mercury concentration in gas exhausted from a cement kiln of the cement manufacturing facility. In case that the mercury concentration in the gas exhausted from the cement kiln of the cement manufacturing facility is high, in the coal ash, unburned carbon with high mercury content can be treated in facilities other than the cement manufacturing facility without feeding the unburned carbon to the cement manufacturing facility, or the quantity of such unburned carbon fed to the cement manufacturing facility cay be adjusted. It is possible to separate mercury from the separated unburned carbon, and utilize the unburned carbon from which mercury is separated in the cement manufacturing facility as a fuel.