Patent ID: 6138588
Filing Date: 2000-10-31
Classification: F23C,F23N

Abstract:
A method for operating a pulverized coal-fired furnace having a combustion chamber operable to combust fuel in a combustion process which produces flue gas and a convection pass through which the flue gas flows upon exiting the combustion chamber, the combustion chamber having four corners each substantially equidistant from adjacent corners such that the combustion chamber has a substantially square cross section and at least one of the four corners of the combustion, chamber having a series of lower compartments for introducing therethrough one of air, fuel and air and fuel into the combustion chamber and at least one upper compartment for introducing air into the combustion chamber comprising the steps of:a) tangentially firing fuel from at least one of the series of lower compartments into the combustion chamber at an offset from a diagonal passing through a pair of opposed corners of the combustion chamber;b) tangentially introducing air from the series of lower compartments into the combustion chamber along a direction which is offset to the diagonal on the same side thereof as the fuel firing offset direction, the collective amount of air tangentially introduced through the lower compartments being less than the stoichiometric amount of air required for complete combustion of the fuel tangentially fired into the furnace such that the fuel and air create a swirling fireball in the combustion chamber;c) injecting air from the at least one upper compartment generally in opposition to the swirling fireball along a direction which is offset to the other side of the diagonal;d) sensing a temperature characteristic of one side of the convection pass, the temperature characteristic varying as a function of the temperature of the one convection pass location;e) determining if the sensed value of the temperature characteristic exceeds an allowable value including comparing the difference between the one convection pass location temperature and a peak temperature to a pre-established buffer difference which represents the smallest acceptable difference between the convection pass location temperature and the peak temperature which can be permitted as the convection pass temperature increases in the direction of the peak temperature;f) in response to a determination that the temperature characteristic exceeds the allowable value, changing the momentum of the air injected through the at least one upper air compartment; andg) after the step of changing the momentum of the air injected through the at least one upper air compartment, sensing the temperature characteristic of the one convection pass location to obtain a post adjustment value of the temperature characteristic and subsequently determining if the post adjustment value exceeds the allowable value and, if the post adjustment value does not exceed the allowable value, iteratively re-sensing the one convection pass location temperature, re-calculating the one convection pass location temperature-to-peak temperature difference to obtain a revised temperature difference, further increasing at least one of a yaw angle and a volume of the air injected by the at least one upper air compartment, and re-comparing the revised temperature difference to the buffer difference until the revised temperature difference is greater than the buffer difference.