Abstract: A boiler operating method operates a boiler by switching between air combustion mode and oxygen combustion mode when burning fossil fuel with first combustion gas and second combustion gas. The second combustion gas compensates for oxygen deficiency in the first combustion gas. The air combustion mode uses air as the first combustion gas and the second combustion gas while the oxygen combustion mode uses mixed gas of combustion flue gas and oxygen-rich gas as the first combustion gas and the second combustion gas, the combustion flue gas being produced when the fossil fuel is burned. By mixing the oxygen-rich gas in the air in the process of switching between air combustion mode and oxygen combustion mode, the air being the first combustion gas used in the air combustion mode, the boiler operating method can switch between the air combustion mode and oxygen combustion mode while maintaining stable combustion.

Abstract: To inhibit corrosion of water wall tubes of a boiler and stabilize combustion on a burner during oxygen combustion operation, a boiler combustion system includes a boiler equipped with a burner and a two-staged combustion gas input port; a flue gas supply fan extracting flue gas from a flue gas treatment system via a flue gas circulation line; a combustion gas supply line, fuel carrier gas supply line, and two-staged combustion gas supply line branched off from the flue gas circulation line downstream of the flue gas supply fan; an oxygen supply line supplying oxygen-rich gas to the combustion gas supply line and fuel carrier gas supply line; combustion air supply fans; a switching unit switching operation between the flue gas supply fan and the combustion air supply fans; and dampers regulating gas flow rates on the combustion gas supply line and the two-staged combustion gas supply line, respectively.

Abstract: An oxygen combustion system includes a boiler to burn fuel using combustion gas composed of oxygen-rich gas and circulating flue gas, a dust remover disposed in a flue through which flue gas discharged from the boiler flows, a second flue leading the combustion gas to the boiler, the combustion gas being made by mixing the circulating flue gas extracted downstream of the dust remover with the oxygen-rich gas, a combustion gas heater exchanging heat between the flue gas flowing between the boiler and dust remover and the combustion gas flowing through the second flue, and a flue gas cooler disposed between the heater and the dust remover to cool the flue gas. A control unit controls at least one of a flow rate and cooling medium temperature of the flue gas cooler such that temperature of the flue gas introduced into the dust remover will be between 90° C. and 140° C.