Patent ID: 8871665

Claim:
A method of regenerating a NO x removal catalyst for removing nitrogen oxide in flue gas at a time of combustion in a boiler by using heavy oil, wherein in a predetermined period of time before shutdown of a boiler, a decomposing step is performed during an operation of the boiler, at which 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 NO x removal device having a NO x removal catalyst 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. to have the NO x removal device in a high-temperature denitration condition, so that vanadyl sulfate (VOSO 4 ) adhering to and accumulating on the NO x removal catalyst is decomposed into vanadium pentoxide (V 2 O 5 ).