To reduce the number of facilities additionally provided for suppressing emission of hazardous substances by mixing organic fuel to be combusted in a supercritical pressure boiler with supercritical pressure water to reform fuel not containing hazardous material, and separating the reformed fuel from the mixture to be supplied in the supercritical pressure boiler.

In a reformer 7, critical pressure water extracted from a supercritical pressure boiler 1 and fuel containing hazardous substances are mixed to separate the hazardous substances therefrom and reform the fuel not to contain hazardous substances. In a separator 7, the mixture of the supercritical pressure water is separated into the reformed fuel, hazardous substances, clean supercritical pressure water having a temperature higher than that when extracted from the supercritical pressure boiler 1. The separated reform fuel is supplied in the supercritical pressure boiler 1 by a reformed-fuel supply device 12. The high-temperature supercritical pressure water is returned to a high-temperature section at an outlet point in a supercritical pressure system 8. Since the reformed fuel is combusted in the supercritical pressure boiler 1, devices such as smoke desulphurizer and dust collector become unnecessary.