CAUTIOUS OPTIMIZATION STRATEGY FOR EMISSION REDUCTION

A system of controlling combustion of fuel in a boiler having an adjustable air-to-fuel ratio. A first sensor is used to measure the CO production to provide a CO distribution range during a period of time for the combustion A second sensor measures the NOx production to provide a NOx distribution range during this period of time for the combustion. A controller adjusts the air-to-fuel ratio to cause combustion of the fuel within the CO distribution range and the NOx distribution range to thereby cause the actual emission for the CO and NOx distributions to average less than the maximum permitted. Preferred time ranges are from 15 to 30 minutes, and the air-to-fuel ratio is selected to produce actual emissions averaging 95% of said maximum.