PURPOSE: To provide a method of operating swirling jet flow bed furnace for combusting EP-ash, according to which temperature of exhaust gas at the outlet of the furnace is kept higher than the dew point of vapor of sulfuric acid contained in the exhaust gas, and the exhaust gas is cooled rapidly through detection of temperature of the subsequent exhaust gas flow, whereby it is enabled to operate the furnace in stable manner, while preventing sticking of dust to the wall of the furnace and inner surface of ducts.

CONSTITUTION: EP-ash is supplied from EP-ash supplying means 8 and it is swirled forcibly together with swirling medium 10 such as sand. Combustible components in the ash are combusted and carbons contained in the ash is also combusted, so that temperature of the gas in the furnace is raised. Temperature of the combustion gas is detected by detector 12 and controlled such that it is 700W730°C in the swirling jet flow bed and 650W700°C at free board section 13. Combustion gas is passed through outlet 14 of the furnace and delivered into duct 15. Cooling air supplying means 16W19 are provided at the top of the furnace for cooling the combustion gas rapidly to about 500°C. By the cooling the combustion gas, compounds having a low melting point, contained in combustion residue, are solidified, so that sticking of the residue to the wall of the furnace or other portions of the system can be prevented