PURPOSE: To efficiently incinerate soot formed with the incineration of EP ash when incinerating soot in exhaust gas, the EP ash, collected by means of a precipitator of an electric precipitator, etc.

CONSTITUTION: EP ash is introduced into a turning fluid-layer furnace 1 from a feed port 2, and agitated by the turning currents and jets of fluid mediums, such as, sand, etc. under high-temperature conditions and incinerated. Exhaust gas enters a single cyclone 4, the first stage precipitator, through a duct 3, and soot is collected and sent into a rotary kiln 5. Meanwhile, exhaust gas exhausted from the single cyclone 4 reaches a multi-cyclone 7, the second precipitator, through a duct 6, and soot collected here is also fed into the rotary kiln 5. Soot is incinerated by mixing soot under a high-temperature condition from the single cyclone 4 and soot with comparatively low temperature from the multi-cyclone 7 and by using an auxiliary combustion burner 8 as necessary.