Effect of Scaling Criteria on Performance of a MILD Furnace

In this study, three scaling criteria including CV, CRT and CK for a laboratory MILD furnace were investigated and the important parameters of MILD combustion including temperature distribution, velocity distribution, flue gas recirculation rate, CO and NOx pollutants for these criteria were compared with a laboratory furnace with internal flue gas recirculation and air preheating as a base case. To determine the distribution of velocity and temperature, the CV and CRT criteria have a better match with the base case than the CK criteria. On the other hand, the pollutants of scale-up furnaces do not match enough with the base case for any criteria, and for the CK and CRT criteria, the amount of pollutants is lower than the base case, especially in the CK criteria. However, because the recirculation rate and temperature distribution are two essential factors in creating MILD combustions; The use of the CRT criteria is suggested for an industrial MILD combustion furnace due to the uniformity in temperature distribution, velocity, flue gas recirculation rate and lower CO and NOx pollutants compared to the laboratory scale. The values of CO and NOx decrease by ۰.۰۵۹ and ۰.۲۵ mg/kWh, respectively, in the CRT criteria compared to the base case.

Keywords:

Scaling criteria , MILD combustion , Constant velocity , constant residence time