Measurements and predictions of nitric oxide and particulates emissions from heavy fuel oil spray flames

Abstract

The results of extensive experimental and predictive studies of nitric oxide (NO) and particulates (unburned coke) emissions from a large-scale laboratory furnace, fired by a heavy fuel oil (HFO) swirl burner with a rotary cup air blast atomizer are presented. A detailed in-flame data archive of gas temperature and O 2 , CO, CO 2 , and NO concentrations has been obtained for five flames for differing excess air levels (15% and 20%), swirl numbers (1.05 and 1.2), primary air-to-fuel ratios (2.5 and 3.0), and atomizer cup speeds (1.0×10 4 and 2.0×10 4 rpm). A wider range of operating parameters has been established to quantify their effects on NO and particulate concentrations at the exit of the furnace. In a parallel modeling study, a two-dimensional computational fluid dynamics code for the prediction of HFO spray combustion and NO and particulates emissions has been constructed. Validation of the code against the experimental data reveals reasonably good quality predictions in the near burner region. The code is capable of simulating the measured trends of flue-gas NO and particulates emissions with useful precision for a wide range of atomizer/burner operating conditions. A scrutiny of the in-flame and flue-gas data, with the aid of the predictions, has provided an enhanced understanding of combustion and combined NO/particulate emissions characteristics of the HFO flames generated by the rotary cup atomizer and establishes the foundation for future work in optimizing combustion and emissions performance.