Experimental study on the combustion and emission characteristics of sludge pyrolysis gas/ammonia premixed swirl flames

To reduce fossil fuel consumption, blending sludge pyrolysis gas and ammonia (NH3) for combustion enables the energy utilization of sludge pyrolysis gas while improving combustion characteristics of NH3. This study employs chemiluminescence to investigate the structure of sludge pyrolysis gas/ammonia/air flame for the first time. A thorough investigation was conducted into the impacts of various swirl structure parameters on the stable combustion range and pollutant emissions. To further reduce pollutant emissions, staged combustion was used, and the effects of ammonia doping ratio, secondary air equivalence ratio, and secondary air inlet height on pollutant emissions were analyzed. The findings demonstrate that increasing the ammonia ratio narrows stable combustion equivalence ratio range. Additionally, at a thermal power of 5 kW, stable combustion was observed in the equivalence ratio range of 0.41-1.70, an improvement of 95.5%. Notably, staged combustion significantly reduced NO emissions, achieving concentrations as low as 32.7 ppm under stoichiometric conditions, compared to 1912.6 ppm in non-staged pure NH3 combustion. This study provides valuable insights into the stability and emission characteristics of sludge pyrolysis gas/ammonia swirl burners for efficient and cleaner low-carbon fuels utilization.