Abstract: In a petroleum residuum burning boiler including: a high-temperature reduction combustion chamber to which petroleum residuum fuel and primary combustion air are supplied and in which combustion is performed at a temperature of 1,300° C. or more and an air ratio of less than one; and a low-temperature oxidation combustion chamber which is connected to the high-temperature reduction combustion chamber and in which combustion is performed at a temperature of less than 1,300° C. and an air ratio of one or more, an assist gas is supplied to the high-temperature reduction combustion chamber, and unburned carbon of a combustion gas of the petroleum residuum fuel is gasified by a water gas reaction by using steam, generated by combustion of the assist gas, as a gasifying agent.

Abstract: In a low NOx boiler of the present invention, a high-temperature reductive combustion zone is provided to an upper portion of a rectangular combustion chamber, and a second-step combustion zone is provided to a middle stage of the combustion chamber. A wall provided below the second-step combustion zone is tapered to narrow the combustion chamber, with a taper angle of approximately 35° or so, relative to a vertical line. An ash discharge port is provided to a furnace bottom portion, and a gas outlet port communicated with a rear pass is provided to a lower side face of the second-step combustion zone. This rear pass is connected with a further post-treatment step, via a super-heater tube and an economizer.

Abstract: In a low NOx boiler of the present invention, a high-temperature reductive combustion zone is provided to an upper portion of a rectangular combustion chamber, and a second-step combustion zone is provided to a middle stage of the combustion chamber. A wall provided below the second-step combustion zone is tapered to narrow the combustion chamber, with a taper angle of approximately 35° or so, relative to a vertical line. An ash discharge port is provided to a furnace bottom portion, and a gas outlet port communicated with a rear pass water wall is provided to a lower side face of the second-step combustion zone. This rear pass water wall is connected with a further post-treatment step, via a super-heater tube and an economizer.