Experimental investigation on oxygen diluted partially premixed and oxygen enriched supplemental combustion for low emission

Highlights: • A new oxygen adjustment method for reducing NOx emission is proposed and tested experimentally. • The relationship between the NOx (CO) emission and operating parameters are obtained. • The effect degrees of the operating parameters on NOx and CO emission are evaluated. • The optimal operating parameters are acquired through Response Surface Method for applications. As one of the main sources of the air pollution, the NOx emission from combustion is difficult to avoid. In this research, a combustion method, named as Oxygen Diluted Partially Premixed and Oxygen Enriched Supplemental Combustion (ODPP/OESC) was proposed to reduce the NOx generation by adjusting the oxygen concentration. The relationships between the operating parameters were deduced. The effects of the ODPP/OESC on the NOx and CO emission were evaluated experimentally. Design of Experiments (DoE) was conducted to obtain the optimal operating parameters through the Response Surface Methodology (RSM). Further statistical analysis indicated that as the dominant operating parameter, the lower oxygen mole fraction of oxygen diluted air (Y_od) resulted in lower NOx but higher CO emission. The Y_od makes the most contribution to the NOx and CO emission, then the oxygen mole fraction of oxygen enriched air (Y_oe) does, and the equivalence ratio of premixed gas (ER_p) does the least. The regression analysis yielded two relationships between the NOx(CO), Y_od, Y_oe, and ER_p. The optimal operating parameters were obtained by the RSM and verified experimentally. NOx and CO emission were 22.6 mg/m³ and 362 mg/m³ under the optimal condition, respectively. So the ODPP/OESC was promising and feasible for the low emission of the CH₄/air combustion and the RSM can be used to control the combustion emissions.