Reduction of NO during load change through the operations of a 2MWth PFBC unit

PFBC improves thermal efficiency of coal-fired power plants and pressurization promotes desulfurization in the fluidized-bed combustor. NO emission is highly dependent on stoichiometric ratio of air to the fuel while the large dead volume in the pressure vessel tends to interfere the quick load change. Therefore, 2MWth PFBC combustion test unit has been operated to investigate load change characteristics of PFBC power generation plants. In the steady-state operations, a wide variety of coal was successfully burned by the 2MWth PFBC test unit. Coal burnout and SO{sub 2} capture exceeded 99% and 90%, respectively while NO emission was kept less than 150ppm. In order to meet more stringent NO reduction, NH{sub 3} was infected into the freeboard of the fluidized bed combustor. NH{sub 3} injection reduced NO emission to as low as 70ppm at the full load. Delay of air feed response was realized by the on-line calculation of the pressure vessel model by the work station. This work station also calculated the performance of the PFBC test unit as a power generation plant. PFBC combustion model including NO reaction kinetics was proposed. The model was demonstrated by comparing the calculated results with the observed data. During the load change, themore » amount of NH{sub 3} injected was controlled by two different method. In one method, the amount of NH3 was controlled based on the actual NO measurement at the stack while, in the other method, based on the estimated NO emission by the combustion model.« less