Application of Premix Combustion to High Input Burner Systems

Premixing of fuel and air has traditionally been avoided on large, high input burner systems. Issues surrounding premix handling and explosion prevention have until recently limited the firing of premix to small burners. North American Mfg. Co. has developed and patented a technique for accomplishing lean premix operation in a fuel staged system that alleviates these prior concerns while simultaneously obtaining the low emission performance associated with this technology. Field operation of two different applications are discussed. The first, a 62.5 x 10^6 Btu/ hr boiler, has been in operation for over one and a half years with no operational problems. This system has consistently demonstrated NOx emissions below 15 ppmv at 3% O2 during low excess air operation. Data from a process heater application is also presented with NOx emissions below 10 ppmv at 3% O2. The input of this application was 120 x IO^6 Btu/hr firing with 60% excess air. Both systems are single burner applications.