Patent ID: 7077069

Claim:
A method of operating a U-type slag-tap firing boiler, comprising: forming a combustion furnace in a volume so that a temperature of a gas flowing through a slag screen separating a combustion furnace and a radiant furnace disposed below the combustion furnace is maintained in a temperature range that ensures a normal functioning of the slag screen even if an air is supplied through a burner into the combustion furnace at an air ratio below 1, and no additional air is supplied, the volume of the combustion furnace being in a range of about 55% to 60% of a volume of a combustion furnace which is formed which is formed above the slag screen and is designed so that an air ratio at the slag screen is approximately 1 so as to achieve a complete combustion of a pulverized coal in the combustion furnace; supplying an air through the burner into the combustion furnace such that the air ratio is below 1; burning a pulverized coal in a fuel-rich combustion mode in the combustion furnace to create a reducing atmosphere substantially throughout the combustion furnace from the burner to the slag screen; and heating an interior of the combustion furnace at a temperature around a fluid temperature, so as to reduce NO x generation.