COMBUSTION METHOD TO PREVENT CONTAMINATION OF COMBUSTION CHAMBER OF PETROLEUM RESIDUE FIRED BOILER

PROBLEM TO BE SOLVED: To provide a combustion method to prevent contamination of a combustion chamber of a petroleum residue fired boiler, capable of preventing degradation of heat exchanging performance and contamination of the combustion chamber due to attachment of melted combustion ash including vanadium oxide to a water pipe of the combustion chamber, when deteriorated fuel such as petroleum residue of high content of vanadium is used as a fuel.SOLUTION: In the combustion chamber 1 including a high-temperature reduction combustion zone 2 having a throttle section 4 at its outlet, and a low-temperature oxidation combustion zone 3 having a cooling section 9 in a region from the throttle section 4 of the high-temperature reduction combustion zone to a position of an air supply nozzle 7 for two-stage combustion, an average gas temperature in the high-temperature reduction combustion zone 2 is within a range of 1,450-1,550°C, and the air for two-stage combustion is supplied when an exhaust gas temperature of the reduction combustion zone is cooled to 1,200-1,350°C at the cooling section 9 to perform the combustion in an oxidation atmosphere, thus a ratio of a component of low-melting point in the vanadium oxide is reduced.