Patent ID: 8413596

Claim:
An oxyfuel boiler having a furnace configured such that oxygen separated from air is mixed with a portion of combustion flue gas branched from combustion flue gas discharged from the boiler, which burns fuel coal to generate steam to be supplied to a steam demand equipment, so as to form oxidizing gas for burning coal, and the oxidizing gas is supplied to the boiler, characterized in that the oxyfuel boiler is further comprising: an oxygen separation apparatus to produce oxygen by separating oxygen from the air, a recirculation fan to supply a portion of combustion flue gas branched from the combustion flue gas discharged from the boiler to the oxyfuel boiler, a temperature sensor disposed at a boiler outlet in the oxyfuel boiler to detect gas temperature of the combustion flue gas, and a control apparatus to calculate gas temperature of the combustion flue gas at the furnace outlet in the boiler from the gas temperature of the combustion flue gas at the boiler outlet detected by the temperature sensor and control the operating condition of the recirculation fan so that the calculated gas temperature of the combustion flue gas at the furnace outlet becomes a desired preset gas temperature.