Oxygen-enriched nonlinear combustion control for low-NOX emissions in natural gas-fired ceramic kilns

Natural gas has great potential for reducing pollutants but has drawbacks in ceramic kilns: poor temperature uniformity, high energy consumption, and significant NO X emissions. This study aims to resolve the trade-off between energy savings from oxygen-enriched combustion and the associated NO X increase by integrating nonlinear combustion technology. A pilot-scale experimental platform for oxygen-enriched nonlinear combustion was built, with oxygen concentration 21%–33%, period 4–20 s, and amplitude 15–35. Experimental results showed that in linear oxygen-enriched combustion, NO X emissions rose with oxygen concentration and furnace temperature, while CO emissions dropped sharply. Temperature and fuel supply rate had more obvious effects on NO X generation. After introducing nonlinear combustion, NO X emissions were effectively suppressed by properly adjusting the combustion period and amplitude. However, for oxygen-enriched nonlinear combustion technology, the emission reduction effect is the best at 24% O 2 . Compared with linear 21% and 24% oxygen combustion, the NO X emissions are significantly reduced, respectively. Response Surface Methodology optimized parameters, achieving a minimum 125.79 ppm NO X , 40.4% below national standards. This study holds significant importance for the achievement of low NO X emissions and energy conservation goals in natural gas-fired ceramic kilns. • Compared with conventional combustion, temperature and fuel input exert stronger effects under oxygen-enriched combustion. • At 24% O 2 , a period of 16 s, and an amplitude of 15 yields the best NO X reduction (64.1% lower than linear combustion). • At 30% O 2 , the minimum NO X emission under the proposed mode achieves a 40.4% reduction relative to the national standard.