METHOD OF REGENERATING NOx REMOVAL CATALYST AND METHOD OF OPERATING HEAVY-OIL FIRED COMBUSTION APPARATUS

A method of operating a heavy-oil fired combustion apparatus that burns heavy oil in a boiler, wherein

• at an operating step before shutdown of a boiler, a part of combustion gas that has bypassed an economizer provided in a flue gas duct for flue gas from the boiler is supplied to an upstream of a NOx removal device and mixed with flue gas from the economizer, a temperature of mixed gas is increased to a predetermined temperature equal to or higher than 360° C., which is higher than a normal operating temperature condition, to have the NOx removal device in a high-temperature denitration condition, so that nitrogen oxide in flue gas is removed during an operation of the NOx removal device, and vanadyl sulfate (VOSO4) adhered and accumulated on a NOx removal catalyst is decomposed into vanadium pentoxide (V2O5), and
• sulfur oxide (SOx) produced at a time of decomposing vanadyl sulfate (VOSO4) into vanadium pentoxide (V2O5) at the operating step before shutdown is treated in an air pollution control facility on a downstream side of the NOx removal device.