Abstract: A combustion control method wherein manipulated variables or the amounts of fuel and air in at least one combustion zone of a boiler are regulated so that both the amount of nitrogen oxides and the amount of unburned coal in the ash at an outlet of a burner furnace or at least one of them passes the regulation standards and satisfies the requirements for operating a plant.

Abstract: This invention relates to the supervision of a combustion state of a combustion furnace. A flame formed concentrically with the direction of a fuel jetted from a burner being the center is measured from its side, and two oxidizing flame zones as high luminance zones are extracted. Using the shape parameters of the flame, an index for reducing NOx and unburnt components in ash are calculated and estimated so as to supervise the combustion state. The positions or centroids of the flames and the distance between the centroids are used as the shape parameters, and the flame shape is divided into two zones for easy display of each zone.